Coordinated by CRHEA-CNRS research laboratory, this monthly newsletter is produced by Knowmade with collaboration from the managers of GANEX groups. The newsletter presents a selection of newest scientific publications, patent applications and press releases related to III-Nitride semiconductor materials (GaN, AlN, InN and alloys)
All issues on www.ganex.fr in Veille section. Free subscription http://www.knowmade.com/ganex
GANEX
Cluster of Excellence (Labex, 2012-2019) GANEX is a cluster gathering French research teams involved in GaN technology. The objective of GANEX is to strengthen the position of French academic players in terms of knowledge and visibility, and reinforce the French industrials in terms of know-how and market share. www.ganex.fr
KnowMade KnowMade is a Technology Intelligence and IP Strategy consulting company specialized in analysis of patents and scientific information. The company supports R&D organizations, industrial companies and investors in their business development by helping them to understand their competitive environment, follow technology trends, and find out opportunities and threats in terms of technology and patents. Knowmade operates in the following industrial sectors: Compound Semiconductors, Power Electronics, RF & Microwave Technologies, LED/OLED Lighting & Display, Photonics, Memories, MEMS & Sensors, Manufacturing & Advanced packaging, Batteries & Energy management, Biotechnology, Pharmaceuticals, Medical Devices, Medical Imaging, Agri-Food & Environment. Knowmade’s experts provide prior art search, patent landscape analysis, scientific literature analysis, patent valuation, IP due diligence and freedom-to-operate analysis. In parallel the company proposes litigation/licensing support, technology scouting and IP/technology watch service. Knowmade’s analysts combine their technical and patent expertise by using powerful analytics tools and proprietary methodologies to deliver relevant patent analyses and scientific reviews. www.knowmade.com
GANEX Newsletter No. 83 December 2019
III-N Technology
GaNEX | III-N Technology Newsletter No. 83 | 2
METHODOLOGY
Each month
150+ new scientific publications
200+ new patent applications
30+ new press releases
Sources 10+ scientific journal editors
Elsevier, IOP, IEEE, Wiley, Springer, APS, AIP, AVS, ECS, Nature, Science …
10+ specialist magazines Semiconductor Today, ElectoIQ, i-micronews,
Compound Semiconductor, Solid State Technology … 5+ open access database: FreeFulPDF, DOAJ …
Patent database: Questel-Orbit
Selection by III-N French
experts
GANEX monthly newsletter
GaNEX | III-N Technology Newsletter No. 83 | 3
TABLE OF CONTENTS (clickable links to chapters)
SCIENTIFIC PUBLICATIONS ............................................................................................................................. 4
GROUP 1 - LEDs and Lighting ................................................................................................................................. 4
GROUP 2 - Laser and Coherent Light ................................................................................................................... 13
GROUP 3 - Power Electronics .............................................................................................................................. 17
GROUP 4 - Advanced Electronics and RF ............................................................................................................. 25
GROUP 5 – MEMS and Sensors............................................................................................................................ 31
GROUP 6 - Photovoltaics and Energy harvesting................................................................................................. 36
GROUP 7 - Materials, Technology and Fundamental .......................................................................................... 40
PRESS RELEASE ............................................................................................................................................ 54
PATENT APPLICATIONS ................................................................................................................................ 76
GaNEX | III-N Technology Newsletter No. 83 | 4
SCIENTIFIC PUBLICATIONS Selection of new scientific articles
GROUP 1 - LEDs and Lighting Group leader: Benjamin Damilano (CRHEA-CNRS)
Information selected by Benjamin Damilano and Mathieu Leroux (CRHEA-CNRS)
Fabrication of relaxed InGaN pseudo-substrates
composed of micron-sized pattern arrays with high
fill factors using porous GaN Electrical & Computer Engineering Department, University
of California Santa Barbara, Santa Barbara, CA 93106,
United States of America
Materials Department, University of California Santa
Barbara, Santa Barbara, CA 93106, United States of
America
Semiconductor Science and Technology
https://doi.org/10.1088/1361-6641/ab4372
Fully or partially relaxed micron-sized InGaN patterns
with fill factors up to 69% were demonstrated via
porosification of the underlying GaN:Si layer. The
impact of the porosification etch conditions and the
pattern geometry on the degree of InGaN relaxation
were studied and monitored via high resolution x-ray
diffraction reciprocal space maps. Additionally, a 45
nm redshift in the photoluminescence emission from
In x Ga1−x N/ In y Ga1−y N multi-quantum wells
(MQWs) regrown on bi-axially relaxed InGaN buffer
layers was observed when compared to a co-loaded
reference sample grown on GaN. The longer emission
wavelength was associated with higher indium
incorporation into the InGaN layers deposited on the
InGaN base layers with a lattice constant larger than
GaN, due to the reduced lattice mismatch between
MQW and InGaN base layer, also called
compositional pulling effect.
Review on Optimization and Current Status of
(Al,In)GaN Superluminescent Diodes Institute of High Pressure Physics PAS, Warsaw, Poland
Kyoto University, Kyoto, Japan
TopGaN Ltd., Warsaw, Poland
ECS J. Solid State Sci. Technol.
https://doi.org/10.1149/2.0282001JSS
Superluminescent diodes represent a device type
which can fill the gap between light emitting diodes
(LEDs) and laser diodes. The light generation based
on Amplified Spontaneous Emission promotes high
brilliance of the light source (better than in case of
LEDs), and by this efficient light harnessing e.g.
coupling to optical fibers. At the same time the low
time coherence of the light reduces the interference
effects, unfavorable in applications such as Optical
Coherence Tomography or in direct image projection.
This article reviews the development process and the
current status of nitride superluminescent diodes,
from their first introduction in 2009 until present.
Formation mechanism and separation of the
mesoporous GaN Distributed Bragg reflectors from
sapphire substrate School of Science, Xi'an Polytechnic University, Xi'an,
710048, People's Republic of China
School of Microelectronics, Shandong University, Jinan,
250100, People's Republic of China
Materials Research Express
https://doi.org/10.1088/2053-1591/ab400d
The mesoporous GaN (MP-GaN) Distributed Bragg
reflectors (DBRs) with tunable spectral stop-band
across visible spectrum are fabricated by
electrochemical etching in the neutral solution. The
formation mechanism of MP-GaN layer in the DBR is
first studied via the differential interference contrast
microscopy. Then the self-standing MP-GaN DBR is
first separated from the sapphire substrate via an
annealing technology, and is transferred to a foreign
substrate. The transferred MP-GaN DBR with high
quality presents high reflectivity (>90%) and large
stop-band widths (>100 nm). And the improved
crystalline quality is due to the reduced defect
density and the total stress relaxation of the GaN
film. The high reflectivity and good crystalline quality
render the lift-off MP-GaN DBR a promising
application prospect in flexible optoelectronic
devices.
GaNEX | III-N Technology Newsletter No. 83 | 5
Progress in High Performance III-Nitride Micro-Light-
Emitting Diodes Materials Department, University of California, Santa
Barbara, California 93106, USA
Department of Electrical and Computer Engineering,
University of California, Santa Barbara, California 93106,
USA
ECS J. Solid State Sci. Technol.
https://doi.org/10.1149/2.0302001JSS
The developments of high performance InGaN based
micro-light-emitting diodes (μLEDs) are discussed.
We first review the early demonstrations of μLEDs
and the state-of-the-art outstanding achievements on
the emerging high-quality display and visible-light
communication applications. Due to the miniature
dimensions of μLEDs, the key understandings and the
significant device advancements to achieve excellent
energy efficiency are addressed. Lastly, two other
critical challenges of μLEDs, namely full-color scheme
and mass transfer technique, and their potential
solutions are explored for future investigations.
Active Efficiency as a Key Parameter for
Understanding the Efficiency Droop in InGaN-Based
Light-Emitting Diodes Department of Photonics and Nanoelectronics, Hanyang
University ERICA, Ansan, Gyeonggi-do 15588, Korea
Department of Electronics and Communication
Engineering, Hanyang University ERICA, Ansan, Gyeonggi-
do 15588, Korea
EtaMax Co. Ltd., Suwon, Gyeonggi-do 16648, Korea
ECS J. Solid State Sci. Technol.
https://doi.org/10.1149/2.0312001JSS
In this paper, we aim to understand the
interrelationships between current, voltage, radiant
power, and eventually, the power efficiency (PE) of
InGaN-based blue light-emitting diodes (LEDs) at high
injection currents. For this purpose, we first
summarize the terms and definitions of various LED
efficiencies. It is essential to measure each efficiency
to understand the physics behind the LED operation
and improve the device performance further. Here,
we show how to measure various LED efficiencies
with physically measurable quantities of the radiant
power, current, voltage, and spectrum of the LED
device. Both the internal quantum efficiency (IQE)
and the voltage efficiency (VE) are interrelated with
the carrier recombination processes. The newly
introduced active efficiency (AE) captures the effects
of the active-layer quality on the IQE and the VE
simultaneously. A novel method of measuring the IQE
just at room temperature, so-called the room-
temperature reference-point method, enables the
measurement of the IQEs of many LED chips,
highlighting the importance of the AE. Using the
experimental IQE curve, it is possible to separate the
total injection current into the radiative and
nonradiative recombination currents. A trade-off
relationship between the IQE and the VE and its
common origins are revealed by this approach.
Recent Advances and Challenges in Indium Gallium
Nitride (InxGa1-xN) Materials for Solid State Lighting Department of Physics, Government Degree College for
Women, Kathua, Jammu and Kashmir-184102, India
Department of Physics, University of Jammu, Jammu and
Kashmir-180006, India
Department of Mechanical System Engineering, Graduate
School of Science and Engineering, Yamagata University,
Yonezawa, Yamagata 992-8510, Japan
ECS J. Solid State Sci. Technol.
https://doi.org/10.1149/2.0292001JSS
In recent times, the demand for electrical energy is
increased to such an extent that the scientific
research has to be focused on the development of
materials that fulfil the growing demands of energy
for efficient solid state lighting purposes and provide
clean and green energy to mitigate the alarming
effects of climate change. The ternary Indium Gallium
Nitride (InxGa1-xN) alloys have emerged as the
potential candidate for Solid State lighting as they
inherent such attributes that make them capable for
these applications. In this review, the attributes of
InxGa1-xN alloys have been discussed. The
dependence of bandgap and bowing parameter on
the composition of InxGa1-xN alloys along with
various techniques employed for the growth of these
alloys in bulk and nanostructure forms have been
reviewed. The recent advances in InxGa1-xN based
nanostructures for Solid State lighting have also been
extensively reviewed. The challenges that are to be
overcome for potential use of InxGa1-xN alloys like
phase segregation, unavailability of a suitable
GaNEX | III-N Technology Newsletter No. 83 | 6
substrate, polarization and doping have been
thoroughly highlighted. In the end, the conclusion
and future scope of work on these wonderful classes
of materials has been drawn.
An Enhancement Mode MOSFET Based on GaN-on-
Silicon Platform for Monolithic OEIC Grünberg Research Centre, Nanjing University of Posts and
Telecommunications, Nanjing 210003, China
IEEE Electron Device Letters
https://doi.org/10.1109/LED.2019.2952905
This letter proposes an enhancement mode MOSFET
on GaN-on-silicon LED epitaxial wafer for the first
time. The fabrication processes of the MOSFET are
fully compatible with InGaN/GaN multiple-quantum-
wells (MQWs) diode and include no ion implantation
or additional epitaxial growth. Gate-recess structure
is formed by well-controlled etching to define the
channel area. The bottom and side wall of the recess
are fully covered by the gate metal to improve the
control ability of gate voltage on the channel
conductance. The measurement results indicate
acceptable performance of the MOSFET with
threshold voltage of 6.01 V. Finally, the MOSFET is
serially connected with an LED based on the same
platform and the brightness of LED can be effectively
controlled by the gate voltage according to the
experimental results. Therefore the MOSFET and LED
have been fabricated on the same GaN-on-silicon
platform, which paves way for the monolithic optical
electronic integrated circuit (OEIC).
Improved Reverse Leakage Current in GaInN-based
LEDs with a Sputtered AlN Buffer Layer Faculty of Science and Technology, Meijo University,
Nagoya 468-8502, Japan
Akasaki Research Center, Nagoya University, Nagoya 464-
8603, Japan
IEEE Photonics Technology Letters
https://doi.org/10.1109/LPT.2019.2952106
In this study, the improvement of reverse leakage
current characteristics with a sputtered (SP) -AlN
buffer layer in GaInN-based green light-emitting
diodes (LEDs) has been presented for the first time.
To understand the origin of the improvement, a
detailed review and careful analysis of reverse
leakage current characteristics were performed. The
review and analysis identified that the improvement
was primarily caused by the suppression of variable-
range-hopping process obtained by replacing
conventional low-temperature GaN buffer.
Verification that threading dislocations and V-defects
can enhance the variable-range-hopping process has
been received. We believe that this study will
contribute to the realization of green LEDs with
advantages of high reliability, a long lifetime, and
electrical robustness.
Evidence of trap-assisted Auger recombination in
low radiative efficiency MBE-grown III-nitride LEDs Department of Materials, University of California, Santa
Barbara, California 93106-5050, USA
Department of Applied Physics, KTH Royal Institute of
Technology, Electrum 229, 16440 Kista, Sweden
Laboratoire de Physique de la Matière Condensée, CNRS,
Ecole Polytechnique, IP Paris, 91128 Palaiseau, France
Journal of Applied Physics
https://doi.org/10.1063/1.5096773
By studying low radiative efficiency blue III-nitride
light emitting diodes (LEDs), we find that the ABC
model of recombination commonly used for
understanding efficiency behavior in LEDs is
insufficient and that additional effects should be
taken into account. We propose a modification to the
standard recombination model by incorporating a
bimolecular nonradiative term. The modified model is
shown to be in much better agreement with the
radiative efficiency data and to be more consistent
than the conventional model with very short carrier
lifetimes measured by time-resolved
photoluminescence in similar, low radiative efficiency
material. We present experimental evidence that a
hot carrier-generating process is occurring within
these devices, in the form of measurements of
forward photocurrent under forward bias. The
forward photocurrent, due to hot carrier generation
in the active region, is present despite the lack of any
“efficiency droop”—the usual signature of band-to-
band Auger recombination in high-quality III-nitride
LEDs. Hot carrier generation in the absence of band-
to-band Auger recombination implies that some
other source of hot carriers exists within these low
GaNEX | III-N Technology Newsletter No. 83 | 7
radiative efficiency devices, such as trap-assisted
Auger recombination.
Effect of KOH passivation for top-down fabricated
InGaN nanowire light emitting diodes Department of Microsystems Engineering, Rochester
Institute of Technology, Rochester, New York 14623, USA
Department of Electrical and Microelectronic Engineering,
Rochester Institute of Technology, Rochester, New York
14623, USA
Journal of Applied Physics
https://doi.org/10.1063/1.5123171
Gallium nitride (GaN) nanowire (NW) light emitting
diodes (LEDs) are promising candidates for
microdisplay applications due to smaller dimensions
and potential for novel integration approaches. For
the commonly adopted top-down GaN NW
fabrication, the required dry etching steps tend to
result in surface states, leading to reduced radiative
recombination rates in LEDs. To passivate the surface
and tune the diameter of the NWs, hydroxyl-based
chemicals such as potassium hydroxide (KOH) are
widely used to treat the surface of these
nanostructures. However, studies on the effects of
temperature, concentration, and the damage
recovery aspects of hydroxyl etching of GaN NWs are
very scarce. These etching parameters are of great
importance for device performance. Here, these
effects are explored thoroughly with a focus on the
correlation of InGaN/GaN NW LED performances to
KOH etching temperature, concentration, and time,
together with a fundamental crystallographic
analysis. The KOH concentration resulting in total
removal of the NW base tapering and a collimated
etch profile for InGaN NW LEDs was found to be
0.8 wt. % at a temperature of 45 °C. A 20 min etch at
23 °C with a 0.1 wt. % KOH concentration will remove
surface states from a top-down fabricated NW LED to
recover up to 90% of the peak photoluminescence
(PL) intensity lost by the dry etch step. The oscillation
behavior in PL intensity with regard to the KOH etch
time has been demonstrated in InGaN/GaN NW LEDs
for the first time, which will shed light upon the
design and passivation of these devices for
microdisplays.
High-Bandwidth InGaN Self-Powered Detector
Arrays toward MIMO Visible Light Communication
Based on Micro-LED Arrays Institute for Electric Light Sources, School of Information
Science and Technology, Engineering Research Center of
Advanced Lighting Technology, and Academy of
Engineering and Technology, Fudan University, Shanghai
200433, China
Department of Chemistry, University of Toronto, 80 Saint
George Street, Toronto, Ontario M5S 3H6, Canada
ACS Photonics
https://doi.org/10.1021/acsphotonics.9b00799
This work reports the use of the chip-based GaN-
based micro-LED (μLED) arrays for multifunctional
applications as microdisplay, data transmitters,
photodetectors, and solar cells. The functions of
display and transmitter have been reported, and
particularly, we experimentally demonstrated that
μLED arrays could be used as self-powered, high-
performance, and wavelength-selective
photodetectors (PDs), enabling high-speed multiple-
input multiple-output (MIMO) visible light
communications (VLC) under on–off keying (OOK)
modulation scheme using 405 nm violet laser diodes
(LDs) as transmitters. The optoelectronic and
communication characteristics of the μLED-based PDs
with diameters of 40, 60 and 100 μm were
systematically studied. The optoelectronic analysis
shows superior performances of μLED-based PDs at a
405 nm wavelength compared with other previously
reported GaN-based PDs. Under a bias voltage of −5
V, the comparable peak responsivities of 0.27, 0.31,
and 0.24 A/W, specific detectivities of 1.1 × 1011, 2.3
× 1012, and 2.1 × 1012 cm H1/2 W–1, and linear
dynamic ranges (LDRs) of 152, 162, and 164 dB were
achieved for 40, 60, and 100 μm μLEDs, respectively.
Even at zero-bias, that is, self-powered mode, we
have achieved high peak responsivities of 0.24, 0.29,
and 0.21 A/W, high specific detectivities of 7.5 ×
1012, 1.5 × 1013, and 1.3 × 1013 cm H1/2 W–1, and
high LDR up to 186, 196, and 197 dB for 40, 60, and
100 μm μLEDs, respectively. The μLEDs could also be
used to harvest the optical energy of the system,
working as solar cells. The μLED-based PD arrays
were tested as receivers in the VLC system to
implement high-speed parallel communication, which
yields maximum data rates of 180, 175, and 185
GaNEX | III-N Technology Newsletter No. 83 | 8
Mbps for single 40, 60, and 100 μm μLED-based PDs
at a distance of 1 m with BERs of 3.5 × 10–3, 3.7 ×
10–3, and 3.5 × 10–3, respectively. Furthermore, the
2 × 2 MIMO parallel VLC system was achieved to
increase the VLC data rate, which suggests the
potential of using large μLED-based PD arrays for
multiple Gbps and even Tbps VLC applications.
Heteroepitaxial Growth of High-Quality and Crack-
Free AlN Film on Sapphire Substrate with
Nanometer-Scale-Thick AlN Nucleation Layer for
AlGaN-Based Deep Ultraviolet Light-Emitting Diodes Center for Photonics and Semiconductors, School of Power
and Mechanical Engineering, Wuhan University, Wuhan
430072, China
HC SemiTek Corporation, Suzhou 215600, China
The Institute of Technological Sciences, Wuhan University,
Wuhan 430072, China
Nanomaterials
https://doi.org/10.3390/nano9111634
High-quality and crack-free aluminum nitride (AlN)
film on sapphire substrate is the foundation for high-
efficiency aluminum gallium nitride (AlGaN)-based
deep ultraviolet light-emitting diodes (DUV LEDs). We
reported the growth of high-quality and crack-free
AlN film on sapphire substrate with a nanometer-
scale-thick AlN nucleation layer (NL). Three kinds of
nanometer-scale-thick AlN NLs, including in situ low-
temperature AlN (LT-AlN) NL, oxygen-undoped ex situ
sputtered AlN NL, and oxygen-doped ex situ
sputtered AlN NL, were prepared for epitaxial growth
of AlN films on sapphire substrates. The influence of
nanoscale AlN NL thickness on the optical
transmittance, strain state, surface morphology, and
threading dislocation (TD) density of the grown AlN
film on sapphire substrate were carefully
investigated. The average optical transmittance of
AlN film on sapphire substrate with oxygen-doped
sputtered AlN NL was higher than that of AlN films on
sapphire substrates with LT-AlN NL and oxygen-
undoped sputtered AlN NL in the 200–270 nm
wavelength region. However, the AlN film on
sapphire substrate with oxygen-undoped sputtered
AlN NL had the lowest TD density among AlN films on
sapphire substrates. The AlN film on sapphire
substrate with the optimum thickness of sputtered
AlN NL showed weak tensile stress, a crack-free
surface, and low TD density. Furthermore, a 270-nm
AlGaN-based DUV LED was grown on the high-quality
and crack-free AlN film. We believe that our results
offer a promising and practical route for obtaining
high-quality and crack-free AlN film for DUV LED.
High Temperature and Power Dependent
Photoluminescence Analysis on Commercial Lighting
and Display LED Materials for Future Power
Electronic Modules Department of Electrical Engineering, University of
Arkansas, Fayetteville, Arkansas, 72701, USA
HC SemiTek (Suzhou), 28 Chenfeng Road, Zhangjiagang,
Jiangsu, 215600, P.R. China
Sandia National Laboratories, Albuquerque, New Mexico,
87185, USA
School of Electrical, Computer and Energy Engineering,
Arizona State University, Phoenix, Arizona, USA
Scientific Reports
https://doi.org/10.1038/s41598-019-52126-4
Commercial light emitting diode (LED) materials -
blue (i.e., InGaN/GaN multiple quantum wells
(MQWs) for display and lighting), green (i.e.,
InGaN/GaN MQWs for display), and red (i.e.,
Al0.05Ga0.45In0.5P/Al0.4Ga0.1In0.5P for display) are
evaluated in range of temperature (77–800) K for
future applications in high density power electronic
modules. The spontaneous emission quantum
efficiency (QE) of blue, green, and red LED materials
with different wavelengths was calculated using
photoluminescence (PL) spectroscopy. The
spontaneous emission QE was obtained based on a
known model so-called the ABC model. This model
has been recently used extensively to calculate the
internal quantum efficiency and its droop in the III-
nitride LED. At 800 K, the spontaneous emission
quantum efficiencies are around 40% for blue for
lighting and blue for display LED materials, and it is
about 44.5% for green for display LED materials. The
spontaneous emission QE is approximately 30% for
red for display LED material at 800 K. The advance
reported in this paper evidences the possibility of
improving high temperature optocouplers with an
operating temperature of 500 K and above.
GaNEX | III-N Technology Newsletter No. 83 | 9
Thermal droop in high-quality InGaN LEDs Soraa, Inc., 6500 Kaiser Dr., Fremont, California 94555,
USA
Applied Physics Letters
https://doi.org/10.1063/1.5124123
Thermal droop is investigated in high-quality InGaN
light-emitting diodes (LEDs). To determine whether it
is caused by intrinsic variations in recombination or
by transport effects, photoluminescence and
electroluminescence measurements are compared.
The former does not show signs of pronounced
thermal droop, with a near-constant internal
quantum efficiency and recombination lifetime,
regardless of temperature. In contrast, strong
thermal droop is observed in the latter, pointing to
transport effects as a leading contributor. Finally,
high-efficiency LEDs with near-ideal thermal droop
are demonstrated.
AlN overgrowth of nano-pillar-patterned sapphire
with different offcut angle by metalorganic vapor
phase epitaxy Ferdinand-Braun-Institut, Leibniz-Institut fuer
Hoechstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489
Berlin, Germany
Centre of Nanoscience & Nanotechnology, University of
Bath, Bath, BA2 7AY, UK
Department of Electronic and Electrical Engineering,
University of Bath, Bath, BA2 7AY, UK
Institute of Solid State Physics, Technical University Berlin,
Hardenbergstr. 36, 10623 Berlin, Germany
Leibniz-Institut fuer Kristallzuechtung, Max-Born-Str. 2,
12489 Berlin, Germany
Department of Physics, SUPA, University of Strathclyde,
107 Rottenrow East, Glasgow G4 0NG, UK
Journal of Crystal Growth
https://doi.org/10.1016/j.jcrysgro.2019.125343
We present overgrowth of nano-patterned sapphire
with different offcut angles by metalorganic vapor
phase epitaxy. Hexagonal arrays of nano-pillars were
prepared via Displacement Talbot Lithography and
dry-etching. 6.6 µm crack-free and fully coalesced AlN
was grown on such substrates. Extended defect
analysis comparing X-ray diffraction, electron
channeling contrast imaging and selective defect
etching revealed a threading dislocation density of
about 109 cm-2. However, for c-plane sapphire offcut
of 0.2° towards m direction the AlN surface shows
step bunches with a height of 10 nm. The detrimental
impact of these step bunches on subsequently grown
AlGaN multi-quantum-wells is investigated by
cathodoluminescence and transmission electron
microscopy. By reducing the sapphire offcut to 0.1°
the formation of step bunches is successfully
suppressed. On top of such a sample an AlGaN-based
UVC LED heterostructure is realized emitting at 265
nm and showing an emission power of 0.81 mW at 20
mA (corresponds to an external quantum efficiency
of 0.86 %).
Defect-Tolerant Luminescent Properties of Low InN
Mole Fraction InxGa1-xN Quantum Wells under the
Presence of Polarization Fields Institute of Multidisciplinary Research for Advanced
Materials, Tohoku University, Sendai, Miyagi 980-8577,
Japan
ECS J. Solid State Sci. Technol.
https://doi.org/10.1149/2.0382001JSS
Different from the case of GaN or AlGaN alloys, the
near-band-edge (NBE) emission of quantum wells
(QWs) and even epilayers of InxGa1-xN alloys of low
InN mole fractions (x) exhibits high quantum-
efficiency (QE) against the presence of threading
dislocations (TDs) as high as 109 cm−2. Accordingly
InxGa1-xN alloys are exclusively used as an active
region of green to ultraviolet light-emitting diodes
(LEDs) and laser diodes, as well as the heart of white
LEDs. Here, current understandings on the emission
mechanisms of InxGa1-xN QWs, especially the defect-
tolerant emission probability of localized excitons,
are reviewed. There exist three disadvantages in
obtaining high QE, namely a high density of TDs that
cause the nonradiative recombination, kinetic
immiscibility of In-containing alloys that introduces
high-concentration Shockley-Read-Hall nonradiative
recombination centers (NRCs) consisting of vacancy
complexes, and high internal electric-fields across the
QWs induced by the polarization discontinuities at
heterointerfaces along the c-axis, which decrease the
radiative recombination rate. The use of InxGa1-xN
alloys of low x overcomes such disadvantages with
the aid of In-originated localization effects that
prevent excitons from trapping by TDs or NRCs.
GaNEX | III-N Technology Newsletter No. 83 | 10
Simultaneous observation of short diffusion length
and sufficiently long nonradiative recombination
lifetime at room temperature indicates strong
localization of holes or excitons.
Characteristics of Blue GaN/InGaN Quantum-Well
Light-Emitting Transistor Graduate Institute of Photonics and Optoelectronics,
National Taiwan University, Taipei 10617, Taiwan
Research and Development Center, Epistar Corporation,
Hsinchu 30078, Taiwan
Department of Photonics, National Chiao-Tung University,
Hsinchu 30010, Taiwan
Research Center for Applied Sciences, Academia Sinica,
Taipei 11529, Taiwan
Department of Electrical Engineering, Graduate Institute of
Photonics and Optoelectronics, National Taiwan
University, Taipei 10617, Taiwan.
IEEE Electron Device Letters
https://doi.org/10.1109/LED.2019.2955733
We demonstrate simultaneous electrical and optical
modulations of the first GaN/InGaN quantum-well
light-emitting transistor (QW-LET) which contains an
In0.15Ga0.85N QW in the heavily p-doped
In0.05Ga0.95N base. Unlike GaAs/InGaAs
counterparts, the GaN/InGaN QW-LET has a current
gain (up to 5) and optical power which increase
linearly with the base current. Its emission spectra
are centered at a wavelength of 420 nm and barely
shift with the current injection, in contrast to the
behavior of typical nitride-based LEDs. The unusual
features of this device may be related to the tilted
band profile induced by the polarization field in the
QW and issue of p-type doping.
Visible LEDs: More than Efficient Light OSRAM Opto Semiconductors GmbH, 93055 Regensburg,
Germany
ECS J. Solid State Sci. Technol.
https://doi.org/10.1149/2.0402001JSS
The lighting sector has seen a tremendous technology
revolution in the recent few decades. This process
has been fueled by light emitting diodes (LEDs), when
group-III nitride materials became available for
semiconductor devices by groundbreaking
technological discovery of p-type conductivity in
gallium nitride (GaN). Ever since this Nobel prize
winning discovery, the race of improving the
efficiency and the efficacy of visible LEDs has been
the dominant driving force, enabled by novel designs
and processes to exploit novel materials, to improve
material quality, electrical and thermal resistance,
light extraction and beam shaping. Technology trends
like miniaturization and integration of electronics and
photonics have led LED markets to expand to a
variety of novel application fields, such as
illumination, sensing, healthcare and visualization,
that are far beyond the traditional general lighting
market. Integration of LEDs and other electronic
devices like CMOS transistor or photodiodes adds
novel functionalities in the smallest dimensions.
Performance improvement of AlGaN-based deep
ultraviolet light-emitting diodes with step-like
quantum barriers School of Microelectronics, University of Science and
Technology of China, Hefei, Anhui 230026, People’s
Republic of China
School of Engineering, University of California San Diego,
San Diego, CA 92093, United States of America
Wuhan National Laboratory for Optoelectronics, Huazhong
University of Science and Technology, Wuhan 430074,
China
IEEE Journal of Quantum Electronics
https://doi.org/10.1109/JQE.2019.2956344
AlGaN-based deep ultraviolet light-emitting diodes
(DUV LEDs) still confront many challenges, which is
partially limited by the poor carrier injection in the
active region. Although incorporating a high Al-
composition quantum barrier (QB) may boost carrier
confinement capability, it will aggravate the quantum
confined Stark effect (QCSE) and thus deteriorate the
optical performance. In this work, a DUV LED
structure with step-like QBs has been proposed and
carefully investigated. This unique QB structure
suppresses the electron overflow into the p-side of
the device and benefits the hole injection efficiency
simultaneously, thereby promoting the radiative
recombination rate in the active region. As a result,
the internal quantum efficiency (IQE) and light output
power (LOP) of the DUV LED with step-like QBs are
significantly improved with an enhancement factor of
40% under 60 mA current injection. Therefore, our
GaNEX | III-N Technology Newsletter No. 83 | 11
step-like QB design provides a feasible approach to
the enhancement of the optical performance of DUV
LEDs.
What limits the efficiency of GaN-based
superluminescent light-emitting diodes (SLEDs)? NUSOD Institute LLC, Newark, USA
Optical and Quantum Electronics
https://doi.org/10.1007/s11082-019-2106-3
Gallium-nitride-based SLEDs are attractive light
sources for augmented reality displays and other
applications. However, the electrical-to-optical power
conversion efficiency (PCE) of SLEDs is still far below
the record-high values reported for LEDs. Utilizing
advanced numerical device simulation, this paper
investigates the internal physical processes that
cause the low PCE of SLEDs. The poor hole
conductivity strongly reduces the electrical efficiency,
similar to laser diodes. However, in contrast to laser
diodes, the rising carrier density in the active layers is
identified as main reason for enhanced Auger
recombination that severely limits the internal
quantum efficiency. Design improvement options are
demonstrated.
Internal quantum efficiencies of AlGaN quantum
dots grown by molecular beam epitaxy and emitting
in the UVA to UVC ranges Université Côte d’Azur, CNRS, CRHEA, 06560 Valbonne,
France
CNRS-Université Montpellier 2, L2C, UMR 5221, 34095
Montpellier, France
Journal of Applied Physics
https://doi.org/10.1063/1.5115593
AlyGa1−yN quantum dots (QDs) have been grown by
molecular beam epitaxy on AlxGa1−xN (0001) using a
2-dimensional–3-dimensional growth mode
transition that leads to the formation of QDs. QDs
have been grown for Al compositions y varying
between 10% and 40%. The influence of the active
region design [composition y, QD height, and
bandgap difference (ΔEg) between the AlxGa1−xN
cladding layer and the AlyGa1−yN QDs] is discussed
based on microscopy, continuous wave
photoluminescence (PL), and time-resolved PL (TRPL)
measurements. In particular, increasing y leads to a
shift of the QD emission toward shorter wavelengths,
allowing covering a spectral range in the UV from
332 nm (UVA) to 276 nm (UVC) at room temperature
(RT). The low-temperature (LT) internal quantum
efficiency of the QD ensembles was estimated from
TRPL experiments at 8 K and values between 11% and
66% were deduced. The highest internal quantum
efficiency (IQE)-LT is found for the QDs with higher Al
content y. Then, the PL spectrally integrated intensity
ratios between RT and LT were measured to estimate
the IQE of the samples at RT. The PL ratio is higher for
larger ΔEg, for QDs with y of 0.1 or 0.2, and high PL
intensity ratios up to 30% were also measured for
QDs with larger y of 0.3 and 0.4. RT IQE values
between 5% and 20% are deduced for AlyGa1−yN
QDs emitting in the 276–308 nm range.
Transferable GaN Enabled by Selective Nucleation of
AlN on Graphene for High‐Brightness Violet
Light‐Emitting Diodes The State Key Discipline Laboratory of Wide Band Gap
Semiconductor Technology, Shaanxi Joint Key Laboratory
of Graphene, Xidian University, Xi’an 710071, China
Advanced Optical Materials
https://doi.org/10.1002/adom.201901632
A transferable GaN epilayer is grown on an improved
aluminum nitride (AlN)/graphene composite
substrate. In this study, theoretical calculations using
first‐principles calculations based on density
functional theory are carefully conducted to further
examine the formation mechanism of AlN on
graphene. AlN selectively grows on graphene via its
optimal nucleation site, which leads to the selective
nucleation of AlN on graphene via quasi‐van der
Waals epitaxy. Thus, an AlN composite nucleation
layer is innovatively inserted between graphene and
GaN, using the time‐distributed and
constant‐pressure growth method by metal organic
chemical vapor deposition. Moreover, a high‐quality
GaN epilayer can be grown while ensuring the
successful exfoliation of GaN by overcoming weak
van der Waals forces between the graphene and the
epilayer. The as‐fabricated violet light‐emitting
diodes (LEDs) deliver an ultrahigh light output power.
This method demonstrates the possibility of
achieving a high‐quality vertical structure for LEDs
GaNEX | III-N Technology Newsletter No. 83 | 12
and the ability to mechanically transfer to achieve
flexible lighting.
Enhanced Performance of AlGaN-Based Deep
Ultraviolet Light-Emitting Diodes with Chirped
Superlattice Electron Deceleration Layer Wuhan National Laboratory for Optoelectronics, Huazhong
University of Science and Technology, Wuhan, China
Nanoscale Research Letters
https://doi.org/10.1186/s11671-019-3201-x
AlGaN-based deep ultraviolet (DUV) light-emitting
diodes (LEDs) suffer from electron overflow and
insufficient hole injection. In this paper, novel DUV
LED structures with superlattice electron deceleration
layer (SEDL) is proposed to decelerate the electrons
injected to the active region and improve radiative
recombination. The effects of several chirped SEDLs
on the performance of DUV LEDs have been studied
experimentally and numerically. The DUV LEDs have
been grown by metal-organic chemical vapor
deposition (MOCVD) and fabricated into
762 × 762 μm2 chips, exhibiting single peak emission
at 275 nm. The external quantum efficiency of 3.43%
and operating voltage of 6.4 V are measured at a
forward current of 40 mA, indicating that the wall-
plug efficiency is 2.41% of the DUV LEDs with
ascending Al-content chirped SEDL. The mechanism
responsible for this improvement is investigated by
theoretical simulations. The lifetime of the DUV LED
with ascending Al-content chirped SEDL is measured
to be over 10,000 h at L50, due to the carrier
injection promotion.
GaNEX | III-N Technology Newsletter No. 83 | 13
GROUP 2 - Laser and Coherent Light Group leader: Bruno Gayral (CEA)
Information selected by Knowmade
Ultrahigh Q microring resonators using a single-
crystal aluminum-nitride-on-sapphire platform Department of Electrical Engineering and Computer
Science, University of Michigan, Ann Arbor, Michigan
48105, USA
Raytheon BBN Technologies, Cambridge, Massachusetts
02138, USA
Optics Letters
https://doi.org/10.1364/OL.44.005679
Aluminum-nitride-on-sapphire has recently emerged
as a novel low-loss photonics platform for a variety of
on-chip electro-optics as well as linear and nonlinear
optics applications. In this Letter, we demonstrate
ultrahigh quality factor (Qint) microring resonators
using single-crystal aluminum nitride grown on a
sapphire substrate with an optimized design and
fabrication process. A record high intrinsic Qint up to
2.8×106 at the wavelength of 1550 nm is achieved
with a fully etched structure, indicating a low
propagation loss less than 0.13 dB/cm. Such high Qint
aluminum-nitride-on-sapphire resonators with their
wide bandgap and electro-optical and nonlinear
optical properties is promising for a wide range of
low-power and high-power compact on-chip
applications over a broad spectral range.
Realization of GaN-based gain-guided blue laser
diodes by helium ion implantation School of Materials Science and Engineering, Shanghai
University, Shanghai 201900, People's Republic of China
Suzhou Institute of Nano-tech and Nano-bionics, Chinese
Academy of Sciences, Suzhou 215123, People's Republic of
China
Key Laboratory of Nanodevices and Applications, Chinese
Academy of Sciences, Suzhou 215123, People's Republic of
China
Semiconductor Science and Technology
https://doi.org/10.1088/1361-6641/ab429c
The fabrication process and characteristics of gallium
nitride (GaN) based gain-guided blue laser diodes
(LDs) are studied, in which an ion implantation
process is adopted to confine carrier injection into
the active region. The implantation of helium ions
with an energy of 85 keV, an angle of 0°, and a
dosage of 4.7 × 1014 cm−2 is conducted in the
experiment. The specific contact resistivity of p-type
ohmic contact of implanted sample is determined to
be 2.2 × 10–4 Ω cm2, which is comparable with the
un-implanted sample. Then, both ion-implanted gain-
guided and ridge waveguide LDs are fabricated at the
same time. Similar threshold current density and
slope efficiency are obtained, while the operation
voltage of ion-implanted gain-guided LDs is 0.2 V
lower than the ridge waveguide LDs at 0.56 kA cm−2.
The ridge waveguide LDs show multi-mode operation
after lasing. However, for ion-implanted gain-guided
LDs, the far-field pattern indicates a single lateral
mode operation up to twice of the threshold current,
and the peak optical output power of blue single
mode LDs at 450 nm exceeds 200 mW under pulsed
condition.
Material gain engineering in staggered polar
AlGaN/AlN quantum wells dedicated for deep UV
lasers Institute of Physics, Wroclaw University of Technology,
Wroclaw, Dolnoslaskie Poland 50-370
IEEE Journal of Selected Topics in Quantum Electronics
https://doi.org/10.1109/JSTQE.2019.2950802
Material gain is calculated for polar staggered
AlxGa1-xN/AlN quantum wells (QWs) of various
architectures: i) with a step-like AlyGa1-yN barrier
grown prior the AlxGa1-xN QW, ii) with a step-like
barrier grown on the QW, and iii) with a step-like
barrier grown prior and on the QW. The obtained
results are compared with those obtained for
reference AlxGa1-xN/AlN QWs. With the increase in
Al concentration in the reference QW the gain peak
blueshifts and its strength decreases mainly due to
the Al-related increase in the electron effective mass.
The step-like barrier is able to tune the spectral
position of the gain peak and enhance the gain
strength. For the staggered QWs with step-like
GaNEX | III-N Technology Newsletter No. 83 | 14
barriers grown prior to the QW a blueshift of the gain
peak is observed while a redshift of the gain peak is
observed for QWs with the step-like barrier grown on
the QW. It is shown that a strong material gain in the
260-280 nm spectral range can be achieved with the
staggered AlxGa1-xN/AlN QW with x=30% and 1 nm
thick step-like AlyGa1-yN barrier of high Al
concentration (y=0.7-0.9).
Spectral tomographic imaging with aplanatic
metalens National Laboratory of Solid State Microstructures, Key
Laboratory of Intelligent Optical Sensing and Integration,
Jiangsu Key Laboratory of Artificial Functional Materials,
College of Engineering and Applied Sciences, Nanjing
University, Nanjing, 210093, China
Collaborative Innovation Center of Advanced
Microstructures, Nanjing, China
Research Center for Applied Sciences, Taipei, 11529,
Taiwan, China
Department of Physics, Taiwan University, Taipei, 10617,
Taiwan, China
Graduate Institute of Electronics Engineering, Taiwan
University, Taipei, 10617, Taiwan, China
Light: Science & Applications
https://doi.org/10.1038/s41377-019-0208-0
Tomography is an informative imaging modality that
is usually implemented by mechanical scanning,
owing to the limited depth-of-field (DOF) in
conventional systems. However, recent imaging
systems are working towards more compact and
stable architectures; therefore, developing
nonmotion tomography is highly desirable. Here, we
propose a metalens-based spectral imaging system
with an aplanatic GaN metalens (NA = 0.78), in which
large chromatic dispersion is used to access spectral
focus tuning and optical zooming in the visible
spectrum. After the function of wavelength-switched
tomography was confirmed on cascaded samples,
this aplanatic metalens is utilized to image
microscopic frog egg cells and shows excellent
tomographic images with distinct DOF features of the
cell membrane and nucleus. Our approach makes
good use of the large diffractive dispersion of the
metalens and develops a new imaging technique that
advances recent informative optical devices.
A 271.8 nm deep-ultraviolet laser diode for room
temperature operation Innovative Devices R&D Center, Corporate Research &
Development, Asahi Kasei Corporation, Fuji, Shizuoka 416-
8501, Japan
Center for Integrated Research of Future Electronics,
Institute of Materials Research and System for
Sustainability, Nagoya University, Furo-cho, Chikusa-ku,
Aichi 464-8601, Japan
Graduate School of Engineering, Nagoya University, Furo-
cho, Chikusa-ku, Aichi 464-8603, Japan
Crystal IS, 70 Cohoes Avenue, Green Island, NY 12183,
United States of America
Applied Physics Express
https://doi.org/10.7567/1882-0786/ab50e0
We present a deep-ultraviolet semiconductor laser
diode that operates under current injection at room
temperature and at a very short wavelength. The
laser structure was grown on the (0001) face of a
single-crystal aluminum nitride substrate. The
measured lasing wavelength was 271.8 nm with a
pulsed duration of 50 ns and a repetition frequency
of 2 kHz. A polarization-induced doping cladding layer
was employed to achieve hole conductivity and
injection without intentional impurity doping. Even
with this undoped layer, we were still able to achieve
a low operation voltage of 13.8 V at a lasing threshold
current of 0.4 A.
Multiwavelength GaN‐Based Surface‐Emitting Lasers
and Their Design Principles Department of Electronic Engineering, East China Normal
University, 500 Dongchuan Road, Shanghai 200241, China
Shanghai Institute of Intelligent Electronics & Systems,
Fudan University, 220 Handan Road Shanghai 200433,
China
Annalen der physik
https://doi.org/10.1002/andp.201900308
Dual‐wavelength lasing operations are demonstrated
in GaN‐based vertical‐cavity surface‐emitting lasers
(VCSELs) comprising ingeniously designed asymmetric
InGaN quantum wells (AS‐QWs). The dual laser
modes show exact positive‐correlated polarization
dependences with a high degree of polarization of up
to 98%. By simply tuning the pump energy, the
components and intensity of the laser outputs can be
GaNEX | III-N Technology Newsletter No. 83 | 15
continuously changed, making wavelength selection
and switching available for the GaN‐based VCSELs.
Detailed theoretical analysis and experimental
measurements show that the intensity of optical gain
and the coupling between the active layer and optical
field, namely the electron–photon interaction, as well
as carrier tunneling and photon reabsorption play a
crucial role in the multiwavelength lasing processes.
Moreover, the design principles of the proposed
AS‐QWs and multistacked size‐varied quantum dot
(MS‐QD) active regions are elaborated to provide
guidelines for controllable multiwavelength
emissions in GaN‐based surface‐emitting lasers.
These results not only provide better understanding
of lasing in nitride‐based microcavity systems but also
shed insight into the more fundamental issues of
electron–photon coupling in such systems.
Importantly, such controllable multiwavelength laser
operations may extend nitride‐based VCSELs to
previously inaccessible areas, for example, flip‐flop,
ultrafast switches, and other functional devices such
as Raman lasers and sensors.
In-situ curvature measurements of AlInN/GaN
distributed Bragg reflectors during growths
containing substrate temperature ramping steps Department of Materials Science and Engineering, Meijo
University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya
468-8502, Japan
Graduate School of Engineering and Akasaki Research
Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya
464-8603, Japan
Journal of Crystal Growth
https://doi.org/10.1016/j.jcrysgro.2019.125357
We developed a model for in-situ wafer curvature
values of AlInN/GaN distributed Bragg reflectors
(DBRs) and determined InN mole fractions in the
DBRs with the model. In order to develop the model,
we experimentally investigated contributions of
substrate temperature ramping steps and a GaN
growth step to changes in the in-situ curvature during
the AlInN/GaN DBR growth. We found that an
increase of curvature change at the substrate
temperature ramping steps was explained by an
increase of the epitaxial layer thicknesses. Another
finding was that a strain in the GaN layer at the GaN
layer growth step was almost zero. Finally, we
determined the InN mole fractions in the AlInN layers
by using the model, showing excellent agreements
with the values estimated from ex-situ X-ray
diffraction measurements. The model reveals not
only the entire in-situ curvature change profile but
also the InN mole fraction under the precisely lattice-
matched condition of AlInN/GaN DBRs.
Effects of quantum well thickness and aluminum
content of electron blocking layer on InGaN-based
laser diodes Department of Applied Physics, China Agricultural
University, Beijing, China
State Key Laboratory of Integrated Optoelectronics,
Institute of Semiconductors, Chinese Academy of Science,
Beijing, China
School of Electronic, Electrical and Communication
Engineering, University of Chinese Academy of Sciences,
Beijing, China
Journal of Materials Science: Materials in Electronics
https://doi.org/10.1007/s10854-019-02539-8
The effects of quantum well (QW) thickness and
aluminum content of electron blocking layer (EBL) on
device performance of InGaN-based laser diodes
(LDs) are numerically investigated with LASTIP. It is
found that the device performance of the 3.0-nm-
thick QW LD is the best. The threshold current
increases and the output power at 120 mA decreases
when the QW thickness is too thin or too thick.
Actually, the optical and electrical characteristics of
InGaN-based LDs demonstrate that the optical
confinement factor decreases and optical loss
increases when the QW thickness is too thin. The
stimulated recombination rate decreases due to the
poorer overlap of electron–hole wave functions and
the enhanced polarization-induced built-in electric
field when the well thickness is too thick. Moreover,
the calculation results of LDs with different aluminum
compositions of EBL demonstrate that the
effectiveness of EBL would be enhanced through
increasing aluminum content when the thickness of
QWs decreases, because there is a reduction of
ground-state energy level and the energy difference
between the ground state and the top of the
quantum barrier.
GaNEX | III-N Technology Newsletter No. 83 | 16
Effect of Mg doping concentration of electron
blocking layer on the performance of GaN-based
laser diodes State Key Laboratory of Integrated Optoelectronics,
Institute of Semiconductors, Chinese Academy of Sciences,
Beijing, China
Center of Materials Science and Optoelectronics
Engineering, University of Chinese Academy of Sciences,
Beijing, China
Applied Physics B
https://doi.org/10.1007/s00340-019-7343-4
Performance of InGaN-based laser diodes (LDs) with
different Mg concentrations of electron blocking
layer (EBL) is investigated by simulation and
experimental methods. It is found from the
simulation results that the threshold current
decreases and slope efficiency increases, when the
Mg concentration of EBL increases from 2 × 1018 to
6 × 1019 cm−3; it is attributed to the suppression of
the leakage of electrons and the enhancement of the
injection of holes due to the variation of potential
barrier for them as the increase of Mg concentration
of EBL. These simulation results agree well with the
experimental ones, when the Mg concentration of
EBL is lower than 7.5 × 1018 cm−3. However, it
deteriorates when the Mg concentration increases to
1.2 × 1019 cm−3. It may be due to the increase of the
absorption loss of LDs.
Inhomogeneous Current Injection and Filamentary
Lasing of Semipolar (2021¯) Blue GaN‐Based
Vertical‐Cavity Surface‐Emitting Lasers with Buried
Tunnel Junctions Materials Department, University of California, Santa
Barbara, CA 93106, U.S.A
Department of Electrical and Computer Engineering,
University of California, Santa Barbara, CA 93106, U.S.A
physica status solidi a
https://doi.org/10.1002/pssa.201900718
Blue (202-1) semipolar vertical‐cavity
surface‐emitting lasers with a buried tunnel junction
current aperture are demonstrated under
continuous‐wave operation with a differential
efficiency of 4% and a threshold current of 2.7 mA for
a lasing mode at 452 nm. The effects of the aperture
diameter on these 9λ cavity length devices are
presented, showing that the differential efficiency
increases with aperture size, whereas the threshold
current density remains constant for apertures larger
than 10 μm. Filamentary lasing is observed in the
larger aperture sizes, and it is suggested that this
mode behavior is due to current injection
inhomogeneity across the aperture. This theory is
supported by the correlation between optical
nearfield images and thermal microscopy images.
Study on electronic blocking layer of 403 nm GaN-
based vertical cavity surface emitting lasers Key Laboratory of Opto-Electronics Technology, Ministry of
Education, Faculty of Information Technology, Beijing
University of Technology, Beijing, China
Optoelectronics Letters
https://doi.org/10.1007/s11801-019-9024-2
In order to obtain good optical characteristics in the
GaN-based vertical-cavity surface-emitting laser
(VCSEL), different kinds of AlGaN electron blocking
layers (EBL) were introduced. These were inserted
coherently near the active region to limit electron
leakage into the p-doped side. The research was
conducted by photonic integrated circuit simulator in
three-dimensional (PICS3D). The simulated results
reveal that an EBL can improve the optical
characteristics of a VCSEL effectively. All the
advantages are due to a reduction in the electron
leakage in the quantum wells. While the voltage of
the five-layer EBLs LD is lower than the voltage of the
seven-layer EBLs LD, the output power of the two is
approximately the same, so the five-layer EBLs is the
best choice for comprehensive structure analysis as
the epitaxial structure can be grown more easily on
it.
GaNEX | III-N Technology Newsletter No. 83 | 17
GROUP 3 - Power Electronics Group leader: Frédéric Morancho (LAAS-CNRS)
Information selected by Frédéric Morancho (LAAS-CNRS) and Yvon Cordier (CRHEA-CNRS)
Analysis of the Significant Rise in Breakdown Voltage of GaN HEMTs from Near-Threshold to Deep Off-state Gate Bias Conditions Indian Institute of Technology Madras, India
IEEE Transactions on Device and Materials Reliability
https://doi.org/10.1109/TDMR.2019.2950604
We investigate AlGaN/GaN high electron mobility
transistors with 0.7 μm gate length whose measured
off-state breakdown voltage, VBR, increased from 28
V at gate-source bias, VGS =-4.1 V (near threshold,
VT) to 87-138 V at VGS =-9.5 V (deep off-state); this
VBR rise was accompanied by a positive VT shift of
0.17-0.5 V; devices with larger VT shift showed larger
VBR rise. Our prior work showed that the near-
threshold VBR is due to space-charge limited current,
which is a signature of buffer traps. Our analysis of
the above observations of the present work shows
the following: The deep off-state VBR is due to
impact ionization induced avalanche. The correlation
between VT shift and VBR rise implies that barrier
and/or buffer traps play a role in governing VBR.
Although different models involving surface, barrier
and buffer traps can simulate the combination of
positive VT shift and large VBR rise, DC electric stress
most likely affects the surface and barrier traps but
not buffer traps.
H-terminated polycrystalline diamond p-channel
transistors on GaN-on-Silicon Ecole polytechnique federale de Lausanne, CH-1015
Lausanne, Switzerland
Lake Diamond SA, CH-1015 Lausanne, Switzerland
IEEE Electron Device Letters
https://doi.org/10.1109/LED.2019.2953245
In many semiconductor technologies, including GaN,
the lack of p-channel devices is a major obstacle for
complementary operations. Here, we demonstrate
highperformance polycrystalline diamond p-channel
transistors on GaN-on-Si. Following the optimization
of the microwave-plasma chemical-vapor-deposition
of diamond on GaN, the polycrystalline layer was
hydrogenated to form a 2D hole-gas at the surface,
acting as p-channel. Relying on a rather simple
fabrication process, these devices exhibited excellent
electrical and thermal performances with on-off ratio
of 109, breakdown voltage of 400 V, specific on-
resistance of 84 mΩ ·, and thermal conductivities
higher than 900 W/m·K. The presented hetero-
integration technology provides a promising platform
for future complementary logic operations, gate
drivers, complementary power switch applications
such as integrated power inverters and converters,
simultaneously serving as a very efficient thermal
management solution in high power density
applications.
Suppression of substrate coupling in GaN high
electron mobility transistors (HEMTs) by hole
injection from the p-GaN gate Engineering Department, University of Cambridge,
Cambridge, CB2 1PZ, United Kingdom
Infineon Technologies Americas Corp., El Segundo,
California 90245, USA
Infineon Technologies Austria AG, 9500 Villach, Austria
Applied Physics Letters
https://doi.org/10.1063/1.5121637
GaN-on-Si is a lateral technology and as such it allows
the integration of high voltage High Electron Mobility
Transistors and low voltage devices on the same chip,
thus enabling the miniaturization and reduction of
parasitic inductances. Due to the fact that integrated
devices share a common substrate, the performance
of one device can be significantly affected by the
operation of another. The choice of the substrate
bias is particularly important in the integrated half-
bridge, a popular topology which includes a low- and
a high-side device. A grounded substrate will cause
vertical stress on the high-side device, while a
floating substrate will couple with the high voltage,
resulting in stress on the low-side device. This is
highly problematic as the devices may fail to turn on
or have a significantly increased RON. In this work,
we carefully investigate the substrate coupling of a
GaNEX | III-N Technology Newsletter No. 83 | 18
high-side and low-side device via backgating
measurements. We demonstrate that the unwanted
RON increase in the high side device could be
suppressed by hole injection from the gate, if the
gate is formed of a p-type material.
Modeling of the Impact of the Substrate Voltage on
the Capacitances of GaN-on-Si HEMTs Fraunhofer Institute for Applied Solid State Physics, 79108
Freiburg im Breisgau, Germany
School of Engineering, Macquarie University, Sydney, NSW
2109, Australia
IEEE Transactions on Electron Devices
https://doi.org/10.1109/TED.2019.2948828
Measurement results of the terminal capacitances of
a high-voltage power GaN high-electron-mobility
transistor on a conductive-Si substrate are presented.
These results show significant dependence of these
capacitances on the substrate (or bulk/backside)
voltage. In this article, we enhance the ASM-GaN
compact model, which is a recently selected industry
standard model for GaN devices, to account for this
dependence. A detailed description of the modeling
procedure is presented. Simulation results based on
the enhanced model are in excellent agreement with
measurement results. The model enables the design
of advanced high-voltage GaN power ICs, such as
half-bridges with drivers and logic, on a conductive Si-
substrate, taking capacitive substrate coupling into
account during simulations.
Determination of electronic band structure by
electron holography of etched-and-regrown
interfaces in GaN p-i-n diodes Department of Physics, Arizona State University, Tempe,
Arizona 85287, USA
School of Electrical, Computer and Energy Engineering,
Arizona State University, Tempe, Arizona 85287, USA
Applied Physics Letters
https://doi.org/10.1063/1.5127014
The electrostatic potential variation across etched-
and-regrown GaN p-i-n diodes for power electronics
has been studied using electron holography in a
transmission electron microscope. The potential
profiles have been correlated with the composition
profiles of Mg, Si, and O obtained by secondary ion
mass spectroscopy. Electronic charges obtained from
the potential profiles correlate well with the presence
of Si and O impurities at regrown interfaces. The
overlap of Mg and Si when Mg doped GaN is grown
directly over an etched undoped GaN surface results
in the formation of a highly doped p-n junction. The
introduction of a thin undoped layer over the etched
GaN surface prevents the formation of such a
junction as the regrowth interface is moved away
from the Mg-doped GaN, and results in diodes with
improved reverse leakage currents, close to the best
values of continuously grown p-i-n diodes. Potential
profiles of continuously grown (not etched) p-i-n
diodes are compared to those of etched-and-regrown
diodes.
Ohmic contact to AlN:Si using graded AlGaN contact
layer NTT Basic Research Laboratories, NTT Corporation, Atsugi,
Kanagawa 243-0198, Japan
Applied Physics Letters
https://doi.org/10.1063/1.5124936
We formed a graded-AlGaN contact layer to improve
the Ohmic characteristics of Si-doped AlN. Linear I-V
characteristics were obtained for AlN with the
graded-AlGaN layer, and the current was three orders
of magnitude larger than that for AlN without the
one. The specific contact resistivity decreased with
the increasing thickness of the graded-AlGaN layer.
This was probably due to a reduction in the three-
dimensional negative charge density induced by the
polarization charge in the graded AlGaN layer. A
minimum contact resistivity of 1.4 ×10−2 Ω cm2 was
obtained for a 330-nm-thick graded-AlGaN layer. To
obtain the Ohmic contact, the Si-dopant
concentration (NSi) should be larger than the
negative fixed charge density (ρπ) induced by the
polarization charge. However, the heavily doped
graded-AlGaN layer (NSi=2.4×1019 cm−3) became
semi-insulating due to self-compensation. The results
indicated that reducing ρπ by relaxing the
compositional slope in the graded layer can improve
the Ohmic characteristics.
GaNEX | III-N Technology Newsletter No. 83 | 19
Ultra-low Contact Resistivity of < 0.1 Ω·mm for Au-
free TixAly Alloy Contact on Non-recessed i-
AlGaN/GaN State Key Laboratory of ASIC and System, School of
Microelectronics, Fudan University, Shanghai 200433,
China
School of Microelectronics, Southern University of Science
and Technology (SUSTech)
GaN Device Engineering Technology Research Center of
Guangdong, SUSTech
Laboratory of the Third Generation Semi-conductor,
SUSTech, 518055 Shenzhen, Guangdong, China
IEEE Electron Device Letters
https://doi.org/10.1109/LED.2019.2953077
A robust process for Au-free ohmic contact formation
is demonstrated by a direct contact of TixAly alloy
film on non-recessed i-AlGaN/GaN. Using this novel
TixAly alloy instead of multilayers as contact metals,
an ultra-low contact resistivity of < 0.1 Ω·mm is
achieved for Ti5Al1 alloy on i-AlGaN/GaN after
880°C/60s annealing.
Effect of the High-Temperature Off-State Stresses on
the Degradation of AlGaN/GaN HEMTs Key Laboratory for Wide Band Gap Semiconductor
Materials and Devices of Education, The School of
Microelectronics, Xidian University, Xi’an 710071, China
Electronics
https://doi.org/10.3390/electronics8111339
GaN-based high electron mobility transistors offer
high carrier density combined with high electron
mobility and often require operation at high
frequencies, voltages, and temperatures. The device
may be under high temperature and high voltage at
the same time in actual operation. In this work, the
impact of separate off-state stresses, separate high-
temperature stresses, and off-state stresses at high
temperatures on AlGaN/GaN high electron mobility
transistors (HEMTs) grown on Si substrates was
investigated. The output current and gate leakage of
the device degenerated to different degrees under
either isolated off-state or high-temperature stress.
The threshold voltage of the device only exhibited
obvious negative drift under the action of high-
temperature and off-state stresses. The parameter at
high temperature (or room temperature) before
stress application was the reference. We found that
there was no significant difference in the degradation
rate of drain current and transconductance peak
when the same off-state stress was applied to the
device at different temperatures. It was concluded
that, under the high-temperature off-state electric
field pressure, there were two degradation
mechanisms: one was the inverse piezoelectric
polarization mechanism only related to the electric
field, and the other was the degradation mechanism
of the simultaneous action of temperature and
electric field.
Cascode GaN/SiC: A Wide-Bandgap Heterogenous
Power Device for High-Frequency Applications Electrical Engineering, Stanford University, Stanford,
California United States 94305
Tsinghua University, 12442 Beijing, Beijing China 100084
Stanford University Department of Aeronautics and
Astronautics, 198869 Stanford, California United States
94305-4035
IEEE Transactions on Power Electronics
https://doi.org/10.1109/TPEL.2019.2954322
Wireless power transfer systems and plasma
generators are among the increasing number of
applications that use high-frequency power
converters. Increasing switching frequency can
reduce the energy storage requirements of the
passive elements that can lead to higher power
densities or even the elimination of magnetic cores.
However, operating at higher frequencies requires
faster switching devices in packages with low-
parasitics. Wide bandgap (WBG) power devices like
Gallium Nitride (GaN) and Silicon Carbide (SiC)
devices, have high critical fields and high thermal
conductivity that make them good candidates for
efficient high-voltage and high-frequency operations.
Commercially available GaN and SiC devices have
ratings targeting different applications. Lateral GaN
devices dominate in lower-voltage (<650 V) and high-
frequency applications as they have relatively small
device capacitances (Coss, Ciss), which make them
easy to drive at high frequencies. On the other hand,
vertical SiC devices are often used in higher-voltage
and lowfrequency applications since they have higher
blocking voltages and larger gate charge than their
GaN counterparts. As a result, SiC devices usually
GaNEX | III-N Technology Newsletter No. 83 | 20
require high-power and complicated gate drive
circuitry. Recent work shows that in both GaN and SiC
devices, losses in device Coss can exceed the
conduction losses at high switching frequencies and
relatively high voltages under Zero-Voltage-Switching
(ZVS) conditions. Moreover, the Coss energy loss
(Eoss) per switching cycle increases with frequency in
GaN devices but remains roughly independent of
frequency in SiC devices. This means that at high
frequencies, SiC devices can be preferable due to
their smaller Coss energy loss even when taking into
consideration the complexity of the gate drive circuit.
In this paper, we present a WBG high-voltage cascode
GaN/SiC power device, combining the advantages of
both a GaN and a SiC device - namely, simple gate
drive requirements, ${E_{oss}$ loss per cycle roughly
independent of frequency, and relatively high voltage
blocking capability. Comparing this cascode GaN/SiC
device with a SiC MOSFET and a SiC JFET of similar
voltage ratings and Rds,ON, we find that the inverter
using the cascode GaN/SiC device has the highest
efficiency and simplest auxiliary gate drive circuitry.
Finally, integrating the cascode GaN/SiC device has
the potential benefits of achieving lower Coss losses,
higher device ratings, and better heat removal
capability.
Band alignment of BeO gate dielectric grown by
atomic-layer deposition on AlGaN/GaN HEMTs School of Integrated Technology, Yonsei University,
Incheon 21983, Republic of Korea
Yonsei Institute of Convergence Technology, Incheon
21983, Republic of Korea
Center for Multidimensional Carbon Materials (CMCM),
Institute for Basic Science (IBS), Ulsan 44919, Republic of
Korea
Department of Chemistry, Ulsan National Institute of
Science and Technology (UNIST), Ulsan 44919, Republic of
Korea
Applied Surface Science
https://doi.org/10.1016/j.apsusc.2019.144107
In this study, we demonstrated the band alignment
between a BeO and AlGaN/GaN heterointerface. The
bandgap of the BeO film was measured to be 8.2 ±
0.05 eV by reflection electron energy loss
spectroscopy. A valence band offset of the
BeO/AlGaN interface was determined to be 1.1 ± 0.1
eV by X-ray photoelectron spectroscopy. Based on
the spectral analysis result, the conduction band
offset was calculated to be 3.2 ± 0.1 eV. When BeO
was used as the gate dielectric of an AlGaN/GaN
transistor, the on/off current ratio was improved to
107. The results of the band alignment and electrical
testing open up opportunities for the application of
BeO films to the gate dielectric of GaN-based high-
power devices.
High Voltage Vertical GaN p-n Diodes with
Hydrogen-Plasma based Guard Rings School of Electrical, Computer, and Energy Engineering,
Arizona State University, Tempe, AZ, 85287 USA
Department of Physics, Arizona State University, Tempe,
AZ, 85287 USA
IEEE Electron Device Letters
https://doi.org/10.1109/LED.2019.2954123
This letter demonstrates novel hydrogen-plasma
based guard rings (GRs) for high voltage vertical GaN
p-n diodes grown on bulk GaN substrates by
metalorganic chemical vapor deposition (MOCVD).
The GR structure can significantly improve
breakdown voltages (BV) and critical electric fields
(Ec) of the devices. Not having field plates or
passivation, the p-n diodes with a 9 µm drift layer
and 10 GRs showed BV/on-resistance (Ron) of 1.70
kV/0.65 mΩ·cm2, which are close to the GaN
theoretical limit. Moreover, the device also exhibited
good rectifying behaviors with an on-current of ∼ 2.6
kA/cm2, an on/off ratio of ∼ 10 10, and a turnon
voltage of 3.56 V. This work represents one of the
first effective GR techniques for high performance
kV-class GaN p-n diodes.
Lateral GaN JFET Devices on Large Area Engineered
Substrates U.S. Naval Research Laboratory, Washington, DC 20375,
USA
Qromis, Inc., Santa Clara, Calfornia 95051, USA
ECS J. Solid State Sci. Technol.
https://doi.org/10.1149/2.0091912jss
Lateral GaN-based p-n junction gated field effect
transistor (LJFET) power transistors on large area
substrates were fabricated as a proof-of-concept to
GaNEX | III-N Technology Newsletter No. 83 | 21
evaluate candidate power switching devices that
could be designed with avalanche breakdown
capability. The devices performed to design
specifications aimed at demonstrating a device
suitable for operation in cascode with a normally-off
low-voltage Si based transistor companion. The
maximum current density was 200 mA/mm and
threshold voltage was −30V. Large gate width devices
(40mm) exhibited >1A current. The devices have
blocking capability to 800V. Initial testing of the
switching dynamics indicates low dynamic RON even
with an un-optimized buffer.
Dynamic On-Resistance in GaN-on-Si HEMTs:
Origins, Dependencies, and Future Characterization
Frameworks Electrical Engineering, Stanford University, Stanford,
California United States 94305
ITET, ETH Zurich, Zurich Switzerland 8092
Electrical Engineering, ETH Zurich, Zurich Switzerland 8044
IEEE Transactions on Power Electronics
https://doi.org/10.1109/TPEL.2019.2955656
Gallium nitride high-electron-mobility transistors
(GaN HEMTs) exhibit dynamic on-resistance ( dRon ),
where the on-resistance immediately after turn-on is
higher than the DC value. A proliferation of recent
literature reports dRon , with some publishing an 8×
increase in conduction losses and others finding that
the problem is nonexistent. This variation can be
largely attributed to the standardized double-pulse-
test (DPT) method, which does not specify blocking
time and will ignore any effects that accumulate over
multiple switching cycles. Absent consistent
measurements, designers are left without an
accurate conduction loss estimate in converters with
GaN HEMTs. We discuss the underlying causes of
charge trapping to find the key influences over dRon ,
and show that the DPT technique gives invalid
results. Our measurements validate that each
operating parameter must be independently
controlled and that only steady-state dRon
measurements will predict dRon performance. For
the commercial GaN HEMT tested in this paper, the
worst-case dRon is nearly 2× higher than the DC
resistance at the same temperature, confirming that
accurate dRon characterization remains critical to
predicting converter characteristics. Finally, we
provide a reporting framework for GaN HEMT
manufacturers and methods to estimate conduction
losses in converters with GaN HEMTs.
High ION and ION/IOFF Ratio Enhancement-Mode
Buried p-Channel GaN MOSFETs on p-GaN Gate
Power HEMT Platform Department of Electronic and Computer Engineering, The
Hong Kong University of Science and Technology, Clear
Water Bay, Hong Kong
InnoScience Technology, Zhuhai, China
IEEE Electron Device Letters
https://doi.org/10.1109/LED.2019.2954035
Enhancement-mode (E-mode) buried p-channel GaN
metal-oxide-semiconductor field-effect-transistors (p-
GaNMOSFET’s) with threshold voltage (VTH) of -1.7 V,
maximum ON-state current (ION) of 6.1 mA/mm and
ION/IOFF ratio of 107 are demonstrated on a
standard p-GaN/AlGaN/GaN-on-Si power HEMT
substrate. An oxygen plasma treatment (OPT) was
deployed to the gated p-GaN region where a
relatively thick (i.e. 31 nm) GaN is retained without
aggressive gate recess. The OPT converts the top
portion of the GaN layer to be free of holes so that
only the bottom portion remains p-type while being
spatially separated from the etched GaN surface and
gate-oxide/GaN interface. As a result, E-mode
operation is enabled while a high-quality p-channel is
retained. Multi-energy fluorine ion implantation was
implemented for planar isolation of GaN p-channel
FETs with mesa edges and sidewalls eliminated.
Consequently, high ION/IOFF ratio is obtained.
Two-Step Mesa Structure GaN p-n Diodes with Low
On-resistance, High Breakdown Voltage and
Excellent Avalanche Capabilities
IEEE Electron Device Letters
https://doi.org/10.1109/LED.2019.2955720
Vertical structure GaN power devices fabricated on
freestanding GaN substrates have high potentials in
ideally efficient energy conversion systems. This
letter describes successful acquisition of high
avalanche capabilities for high breakdown voltage
GaN p-n junction diodes. We have already reported
the high avalanche capability by applying a punch-
GaNEX | III-N Technology Newsletter No. 83 | 22
through structure in p-GaN layer, however; the
structure caused a drawback of increase in on-
resistance and turn-on voltage. By applying a newly
developed two-step mesa structure consisting of the
first inner mesa with partially thinned p-GaN layer
and the second outer mesa etched to n-GaN drift
layer, the high avalanche capabilities with reversible
current-voltage characteristics have been realized at
high breakdown voltages of 4.7-4.8 kV without
sacrificing the forward I-V characteristics. The two-
step mesa structure transferred the position of the
peak electric field in the p-n junction from the dry-
etch damaged second outer mesa to the first mesa
covered by the thinned p-GaN layer, which could lead
the mild breakdown. The high avalanche capability
was obtained with good reproducibility regardless of
the anode electrode diameter. This structure can
contribute to the construction of robust power
systems.
Time-dependent characteristics and physical
mechanisms of AlGaN/GaN metal–insulator–
semiconductor high electron mobility transistors
under different bias conditions School of Materials Science and Engineering, The Key
Laboratory of Key Film Materials and Application for
Equipments (Hunan Province), Xiangtan University,
Xiangtan, Hunan 411105, People's Republic of China
Science and Technology on Reliability Physics and
Application of Electronic Component Laboratory, No.5
Electronics Research Institute of the Ministry of Industry
and Information Technology, Guangzhou 510610, People's
Republic of China
School of Electronics and Information Technology, Sun Yat-
sen University, Guangzhou 510275, People's Republic of
China
Journal of Physics D: Applied Physics
https://doi.org/10.1088/1361-6463/ab3d52
We experimentally investigate the time-dependent
degradation of AlGaN/GaN metal–insulator–
semiconductor high electron mobility transistors
subjected to different bias conditions. By means of
the combined performance under OFF/SEMI-ON/ON
state bias conditions, the dependence of threshold
voltage (V th), maximum transconductance (g m) and
saturation drain current (I dsat) on stress mode are
revealed. In the OFF-state, with the high temperature
reverse bias stress, the main mechanism is the
charge-trapping in the gate dielectric layer, leading to
the recoverable negative shift of the V th. In the
SEMI-ON-state, because of the hot-carrier injection,
the hot electrons could break the Si–H bonds,
resulting in the generation of interface states and can
also be captured by the trap states in the AlGaN
barrier or GaN buffer. This effect will cause the
decrease of saturation drain current and an
unrecoverable V th negative shift. In the ON-state,
due to the attenuation of hot electrons effect, V th
hardly changes, while I dsat has a dramatic decrease
caused by the self-heating effect. Low frequency
noise characteristics were used to extract the defect
state density, which then increases by about three
orders of magnitude after SEMI-ON-state stress.
Transmorphic epitaxial growth of AlN nucleation
layers on SiC substrates for high-breakdown thin
GaN transistors Thin Film Physics Division, Department of Physics (IFM),
Linköping University, SE-581 83 Linköping, Sweden
SweGaN AB, Teknikringen 8D, SE-583 30 Linköping,
Sweden
Institute of Electronic, Microelectronic and
Nanotechnology, Av. Poincaré, 59650 Villeneuve d'Ascq,
France
Applied Physics Letters
https://doi.org/10.1063/1.5123374
Interfaces containing misfit dislocations deteriorate
electronic properties of heteroepitaxial wide bandgap
III-nitride semiconductors grown on foreign
substrates, as a result of lattice and thermal
expansion mismatches and incompatible chemical
bonding. We report grain-boundary-free AlN
nucleation layers (NLs) grown by metalorganic
chemical vapor deposition on SiC (0001) substrates
mediated by an interface extending over two atomic
layers L1 and L2 with composition (Al1/3Si2/3)2/3N
and (Al2/3Si1/3)N, respectively. It is remarkable that
the interfaces have ordered vacancies on one-third of
the Al/Si position in L1, as shown here by analytical
scanning transmission electron microscopy and ab
initio calculations. This unique interface is coined the
out-of-plane compositional-gradient with in-plane
vacancy-ordering and can perfectly transform the in-
plane lattice atomic configuration from the SiC
GaNEX | III-N Technology Newsletter No. 83 | 23
substrate to the AlN NL within 1 nm thick transition.
This transmorphic epitaxial scheme enables a critical
breakdown field of ∼2 MV/cm achieved in thin GaN-
based transistor heterostructures grown on top.
Lateral breakdown voltages of 900 V and 1800 V are
demonstrated at contact distances of 5 and 20 μm,
respectively, and the vertical breakdown voltage is ≥3
kV. These results suggest that the transmorphic
epitaxially grown AlN layer on SiC may become the
next paradigm for GaN power electronics.
Solid-State Carbon-Doped GaN Schottky Diodes by
Controlling Dissociation of the Graphene Interlayer
with a Sputtered AlN Capping Layer Department of Materials Science and Engineering, National
Taiwan University of Science and Technology, Taipei 106,
Taiwan
Department of Materials Science and Engineering, Korea
University, Seoul 02841, Korea
Materials and Electro-Optics Research Division, National
Chung-Shan Institute of Science and Technology, Taoyuan
320, Taiwan
ACS Appl. Mater. Interfaces
https://doi.org/10.1021/acsami.9b18976
Carbon-doped GaN (GaN:C) Schottky diodes are
prepared by controlling the destruction status of
graphene interlayer (GI) on the substrate. The GI
without a sputtered AlN capping layer (CL) was
destroyed due to ammonia precursor etching
behavior in a high-temperature epitaxy. The
damaged GI, like nano-graphite as a solid-state
carbon doping source, incorporated the epitaxial
growth of GaN layer. The secondary ion mass
spectroscopy depth profile indicated that the carbon
content in GaN layer can be tuned further by
optimizing the sputtering temperature of AlN CL due
to the better capping ability of high crystalline quality
AlN CL on GI being achieved at higher temperature.
The edge-type threading dislocation density (TDD)
and carbon concentration of the GaN:C layer with an
embedded 550 °C-grown AlN CL on a GI substrate can
be significantly reduced to 2.28x10^9 cm^-2 and
~2.88x10^18 cm^-3, respectively. Thus, a Ni-based
Schottky diode with ideality factor of 1.5 and barrier
height of 0.72 eV was realized on GaN:C. The series
resistance increased from 28 k-ohm at 303 K to 113 k-
ohm at 473 K, while the positive temperature
coefficient (PTC) of series resistance was ascribed to
the carbon doping that induced the compensation
effect and lattice scattering effect. The decrease of
the donor concentration was confirmed by
temperature-dependent capacitance-voltage (C-V-T)
measurement. The PTC characteristic of GaN:C
Schottky diodes created by dissociating the GI as a
carbon doping source should allow for the future use
of high-voltage Schottky diodes in parallel, especially
in high temperature environments.
Enhancement‐Mode AlGaN/GaN Vertical Trench
Metal–Insulator–Semiconductor
High‐Electron‐Mobility Transistors with a High Drain
Current Fabricated Using the AlGaN Regrowth
Technique Graduate School of Engineering, University of Fukui, 3-9-1
Bunkyo, Fukui 910-8507, Japan
physica status solidi a
https://doi.org/10.1002/pssa.201900622
Herein, the first successful fabrication of
enhancement (E)‐mode AlGaN/GaN vertical trench
metal–insulator–semiconductor (MIS)
high‐electron‐mobility transistors (HEMTs) using
n+‐GaN/p‐GaN/n−‐GaN epistructures on
free‐standing n+ substrates is reported. A trench with
smooth semipolar planes (sidewalls) with angles of
45° and 135° from the c‐plane is formed by reactive
ion etching. Using metalorganic vapor‐phase epitaxy,
a uniform thickness of the AlGaN layer is regrown in
the trench. Devices fabricated without Mg activation
treatment for p‐GaN show depletion (D)‐mode
operation. The operation mode is changed from D to
E when Mg activation annealing temperature exceeds
700 °C. A high drain current (ID) ≥ 0.8 A mm−1 is
obtained in the devices with a relatively low Mg
concentration (≤1 × 1018 cm−3), whereas a threshold
voltage (VTH) as high as 22 V is obtained in the
devices with a high Mg concentration
(5 × 1018 cm−3). The poorly controlled VTH with
doped Mg concentration is discussed from the
viewpoint of dehydrogenation of the p‐GaN layer.
GaNEX | III-N Technology Newsletter No. 83 | 24
Study of E-Mode AlGaN/GaN MIS-HEMT with La-
silicate Gate Insulator for Power Applications Department of Electronics Engineering, National Chiao-
Tung University, Hsinchu, Taiwan, ROC
Department of Materials Science and Engineering, National
Chiao-Tung University, Hsinchu, Taiwan, ROC
Institute of Lighting and Energy Photonics, National Chiao-
Tung University, Tainan, Taiwan, ROC
International College of Semiconductor Technology,
National Chiao-Tung University, Hsinchu, Taiwan, ROC
Department of Physical Electronics, Tokyo Institute of
Technology, O-okayama, Meguro-ku, Japan
Journal of Electronic Materials
https://doi.org/10.1007/s11664-019-07790-7
An enhancement-mode (E-mode) AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistor (MIS-HEMT) with La2O3/SiO2 gate insulator is investigated for high power application. The La2O3/SiO2 composite oxide formed amorphous La-silicate after post deposition annealing. Good oxide film quality and excellent La-silicate/AlGaN interface properties were achieved as evidenced by the capacitance–voltage (C–V) curves and hysteresis effect of the La-silicate on AlGaN/GaN metal–oxide–semiconductor capacitors. As a result, the E-mode AlGaN/GaN MIS-HEMT with La-silicate gate insulator shows good threshold voltage (Vth) stability and demonstrated only slightly increase in the dynamic on-resistance (Ron) after high drain bias stress test. The device also exhibits high current density of 752 mA/mm, high maximum transconductance of 210 mS/mm, low subthreshold swing of 104 mV/decade, and ION/IOFF = 107 when tested at VDS = 10 V. Furthermore, low on-resistance of 7.6 Ω mm, high
breakdown voltage of 670 V, and excellent delay time of 4.2 ps were achieved, demonstrating the La-silicate MIS-HEMTs have the potential to be used for power electronic applications. Influence of Oxygen–Plasma Treatment on In-Situ
SiN/AlGaN/GaN MOSHEMT with PECVD SiO2 Gate
Insulator School of Electronic and Electrical Engineering, Hongik
University, Seoul 04066, Korea
Materials
https://doi.org/10.3390/ma12233968
The influence of oxygen–plasma treatment on in situ
SiN/AlGaN/GaN MOS high electron mobility
transistor with SiO2 gate insulator was investigated.
Oxygen–plasma treatment was performed on in situ
SiN, before SiO2 gate insulator was deposited by
plasma-enhanced chemical vapor deposition
(PECVD). DC I-V characteristics were not changed by
oxygen plasma treatment. However, pulsed I-V
characteristics were improved, showing less
dispersion compared to non-treated devices. During
short-term gate bias stress, the threshold voltage
shift was also smaller in a treated device than in an
untreated one. X-ray photoemission spectroscopy
also revealed that SiO2 on in situ SiN with oxygen–
plasma treatment has an O/Si ratio close to the
theoretical value. This suggests that the oxygen
plasma treatment-modified surface condition of the
SiN layer is favorable to SiO2 formation by PECVD.
GaNEX | III-N Technology Newsletter No. 83 | 25
GROUP 4 - Advanced Electronics and RF Group leader: Jean-Claude Dejaeger (IEMN)
Information selected by Jean-Claude Dejaeger (IEMN) and Yvon Cordier (CRHEA-CNRS)
Linearity Improvement with AlGaN Polarization-Graded Field Effect Transistors with Low Pressure Chemical Vapor Deposition Grown SiNx Passivation Department of Electrical and Computer Engineering, The
Ohio State University, Columbus, OH-43210, USA
Qorvo, Inc., Richardson, TX-75081, USA
IEEE Electron Device Letters
https://doi.org/10.1109/LED.2019.2951655
In this letter, we discuss the application of low
pressure chemical vapor deposition (LPCVD) grown
SiNx passivation-first process to improve the power
density and linearity performance of a metal oxide
chemical vapor deposition (MOCVD) grown AlGaN
channel polarization-graded field-effect transistor
(PolFET). Significantly improved dispersion behavior
was observed compared to plasma enhanced
chemical vapor deposition (PECVD) grown SiNx
passivation. The Current collapse at 30 V drain
quiescent condition for pulsed I-V was reduced to 8%
(LPCVD) from 25% (PECVD). 10 GHz load-pull
measurement showed a maximum output power
density of 3.4 W/mm with a peak power added
efficiency (PAE) of 40%. Twotone intermodulation
distortion measurement at 10 GHz for devices with
150..m width revealed an OIP3 of 39 dBm and an
excellent corresponding linearity figure of merit
OIP3/PDC of 13.3 dB. This is the best device level
OIP3/PDC reported to date at Xband for III-Nitride
microwave transistors.
High Performance and Highly Robust AlN/GaN
HEMTs for Millimeter-Wave Operation CNRS-IEMN, Institut d’Electronique, de Microélectronique
et de Nanotechnologie, Villeneuve-d’Ascq, France
IEEE Journal of the Electron Devices Society
https://doi.org/10.1109/JEDS.2019.2952314
We report on a 3 nm AlN/GaN HEMT technology for
millimeter-wave applications. Electrical
characteristics for a 110 nm gate length show a
maximum drain current density of 1.2 A/mm, an
excellent electron confinement with a low leakage
current below 10 μA /mm, a high breakdown voltage
and a F T /F max of 63/300 GHz at a drain voltage of
20V. Despite residual trapping effects, state of the art
large signal characteristics at 40 GHz and 94 GHz are
achieved. For instance, an outstanding power added
efficiency of 65% has been reached at V DS = 10V in
pulsed mode at 40 GHz. Also, an output power
density of 8.3 W/mm at V DS = 40V is obtained
associated to a power added efficiency of 50%. At 94
GHz, a record CW output power density for Ga-polar
GaN transistors has been reached with 4 W/mm.
Additionally, room temperature preliminary
robustness assessment at 40 GHz has been
performed at V DS = 20V. 24 hours RF monitoring
showed no degradation during and after the test.
Improving the transconductance flatness of
InAlN/GaN HEMT by modulating VT along the gate
width Key Laboratory of Wide Band-Gap Semiconductor
Materials and Devices, School of Microelectronics, Xidian
University, Xi'an 710071, People's Republic of China
School of Advanced Materials and Nanotechnology, Xidian
University, Xi'an 710071, People's Republic of China
School of Physics and Optoelectronic Engineering, Xidian
University, Xi'an 710071, People's Republic of China
Applied Physics Express
https://doi.org/10.7567/1882-0786/ab48bf
A modulated V T HEMT with improved g m flatness is
demonstrated for high linearity application. The
modulated V T HEMT was achieved by connecting
two elements with different V T values in parallel
along the gate width, realizing a flat resulting transfer
curve, and the two different V T elements were
fabricated by recessing part area of the barrier along
the gate width under the gate region. The proposed
HEMT shows a gate voltage swing as high as 5.4 V, a
high drain current of approximately 2 A mm−1, and
an f T/f max of 63/125 GHz with a much flatter profile
within the large gate voltage range.
GaNEX | III-N Technology Newsletter No. 83 | 26
X-Band High-Efficiency Continuous Class B Power
Amplifier GaN MMIC Assisted by Input Second-
Harmonic Tuning School of Aeronautics and Astronautics, Zhejiang
University, Hangzhou 310027, China
The Project Management Center, Equipment Development
Department, Beijing 100000, China
Electronics
https://doi.org/10.3390/electronics8111312
This paper presents a high-efficiency continuous class
B power amplifier MMIC (Monolithic Microwave
Integrated Circuit) from 8 GHz to 10.5 GHz, fabricated
with 0.25 μm GaN-on-SiC technology. The Pedro
load-line method was performed to calculate the
optimum load of the GaN field-effect transistor (FET)
for efficiency enhancement. Optimized by an output
second-harmonic tuned network, fundamental to
second-harmonic impedance, mapping was
established point-to-point within a broad frequency
band, which approached the classic continuous class
B mode with an expanded high-efficiency bandwidth.
Moreover, the contribution to the output capacitance
of the FET was introduced into the output second-
harmonic tuned network, which simplified the
structure of the output matching network. Assisted
by the second-harmonic source-pull technique, the
input second-harmonic tuned network was optimized
to improve the efficiency of the power amplifier over
the operation band. The measurement results
showed 51–59% PAE (Power Added Efficiency) and
19.8–21.2 dB power gain with a saturated power of
40.8–42.2 dBm from 8 GHz to 10.5 GHz. The size of
the chip was 3.2 × 2.4 mm2.
Degradation of Ka-Band GaN LNA Under High-Input
Power Stress: Experimental and Theoretical Insights Microsystem and Terahertz Research Center, Institute of
Electronic Engineering, China Academy of Engineering
Physics, Chengdu 610200, China
Department of Physics, School of Science, Wuhan
University of Technology, Wuhan 430070, China
IEEE Transactions on Electron Devices
https://doi.org/10.1109/TED.2019.2947311
A 23-30-GHz gallium nitride (GaN) low-noise amplifier
(LNA) with a noise figure (NF) of 0.87-1.51 dB is
presented in this article. This LNA was fabricated with
100-nm gate-length GaN-on-silicon (GaN/Si)
microwave monolithic integrated circuit (MMIC)
process. The linear gain is 14-17 dB within the band.
For investigating the robustness of this LNA, 1-W
continuous wave (CW) at 27 GHz was stressed on the
input port of the LNA. The gain decreased, and the NF
increased after stress. Experimental research and
first-principles calculations were carried out to
investigate the physical origin of the degradation. The
dehydrogenation of VGa-H3 complexes causes the
decrease of gain, and the creation of VAl-H4in the
AlN barrier is supposed to cause an increase of NF.
Tensile Strain and Fermi Level Alignment in
Thermally Grown TiO2 and Al2O3 Based AlGaN/GaN
MOS-HEMTs Department of Electrical Engineering, Indian Institute of
Technology Bombay, Mumbai 400076, India
Solid-State Electronics
https://doi.org/10.1016/j.sse.2019.107702
This work reports on the origin of performance
improvement for thermally grown TiO2 and Al2O3
based AlGaN/GaN metal-oxide-semiconductor high
electron mobility transistors (MOS-HEMTs). The
oxides have been used as gate dielectrics and
passivation layer. High resolution X-ray diffraction, X-
ray photoelectron spectroscopy, and transistor
characteristics are analysed to investigate the
improvements in the two dimensional electron gas
(2DEG) concentration. The HRXRD analysis reveals
that in-plane tensile stress of AlGaN layer is increased
by 23% (12%) for TiO2 (Al2O3) sample as compared
to that of an as-grown sample. The induced tensile
stress in the AlGaN barrier layer enhances the
piezoelectric polarization charges which effectively
improve the carrier confinement and mobility at the
interface. The improvement in the DC characteristics
is observed as a reduction in the gate leakage current
without deteriorating gate control and
transconductance. The output characteristics of TiO2
(Al2O3) based MOS-HEMTs have shown a 60% (40%)
increment in the maximum saturation drain current
and 50% (40%) increment in the transconductance as
compared to that of a control sample. The RF
characteristics also show similar order of
improvements.
GaNEX | III-N Technology Newsletter No. 83 | 27
High frequency guided mode resonances in mass-
loaded, thin film gallium nitride surface acoustic
wave devices Quantum Engineering Technology Labs and Department of
Electrical and Electronic Engineering, University of Bristol,
Woodland Road, Bristol BS8 1UB, United Kingdom
Center for Device Thermography and Reliability, H.H. Wills
Physics Laboratory, University of Bristol, Woodland Road,
Bristol BS8 1UB, United Kingdom
Applied Physics Letters
https://doi.org/10.1063/1.5123718
We demonstrate high-frequency (>3 GHz), high
quality factor radio frequency (RF) resonators in
unreleased thin film gallium nitride (GaN) on sapphire
and silicon carbide substrates by exploiting acoustic
guided mode (Lamb wave) resonances. The
associated energy trapping, due to mass loading from
gold electrodes, allows us to efficiently excite these
resonances from a 50 Ω input. The higher phase
velocity, combined with lower electrode damping,
enables high quality factors with moderate electrode
pitch and provides a viable route towards high-
frequency piezoelectric devices. The GaN platform,
with its ability to guide and localize high-frequency
sound on the surface of a chip with access to high-
performance active devices, will serve as a key
building block for monolithically integrated RF front-
ends.
Enhancement of Hot Spot Cooling by Capped
Diamond Layer Deposition for Multifinger
AlGaN/GaN HEMTs Department of Mechanical and Aerospace Engineering,
Rutgers University, Piscataway, NJ 08854 USA
Department of Electrical and Computer Engineering,
University of Nebraska, Lincoln, NE 68588 USA
IEEE Transactions on Electron Devices
https://doi.org/10.1109/TED.2019.2951190
The impact of a capped diamond layer for enhanced
cooling of multifinger AlGaN/GaN high-electron-
mobility transistors (HEMTs) has been investigated
under the steady-state operating condition. By
depositing a capped diamond thin film onto the
HEMTs, the temperature distribution around the hot
spots tends to be more uniform and the junction
temperature can be suppressed significantly. The
capped diamond serves as a highly effective heat
spreader, and its thermal spreading ability depends
on the structural design patterns and working
conditions. Some key parameters affecting the
thermal performance of the capped diamond have
been examined, including the heat dissipation power
density, gate pitch distance, embedding depth of the
heat source, thermal boundary resistance, substrate
material, as well as the cap thickness. For the 12-
finger model with 20-μm gate pitch distance and gate
power density of 6 W/mm, a 20-μm layer of capped
diamond could reduce the junction temperature by
12.1% for GaN-on-diamond HEMTs and by 25.3% for
GaN-on-SiC HEMTs. Even with a 1-μm capped
diamond layer, the reduction would be 7.6% and
9.9%, respectively. The temperature reduction for
GaN-on-Si is more significant.
DC and RF Characterization of AlGaN/AlN/GaN/AlN
DH‐HEMT on Sapphire Nano-Optical Engineering, Korea Polytechnic University
(KPU), Siheung, Gyeonggi 427-793, Republic of Korea
School of Electronic and Electrical Engineering, Hongik
University, Seoul 04066, Republic of Korea
Department of Electrical and Computer Engineering, and
Inter-university Semiconductor Research Center, Seoul
National University, Seoul 08826, Republic of Korea
WAVICE inc. 2/F, 46, Samsung 1-ro 5-gil, Hwaseong-si,
Gyeonggi-do, 18449, Republic of Korea
physica status solidi a
https://doi.org/10.1002/pssa.201900695
We introduce the AlGaN/AlN/GaN/AlN
double‐heterostructure high electron mobility
transistor (DH‐HEMT) on sapphire substrate, and
compare its direct current (DC) and radio frequency
(RF) characteristics to the conventional GaN‐based
single‐heterostructure HEMT (SH‐HEMT) on SiC
substrate. The devices having the two‐finger gate
were fabricated with gate width of 200 μm (2 × 100
μm) and gate length of 500 nm. The DC performance
of the DH‐HEMT showed a transconductance of 0.233
S/mm and a maximum drain current density of 0.93
A/mm, comparable to that of the SH‐HEMT. There
was less pronounced kink‐effect in the DC I‐V
characteristics, whereas, the off‐state subthreshold
current was approximately four orders of magnitude
higher than that of SH‐HEMT. A pulsed I‐V
GaNEX | III-N Technology Newsletter No. 83 | 28
measurement showed a greatly suppressed slump
ratio Z1 and Z2 of 1.6 and 4.3% for the DH‐HEMT. It
was shown that the performances of a small and a
large signal characteristics of the DH‐HEMT were
equivalent to the GaN SH‐HEMT: the current gain
cut‐off frequency (fT) and the maximum oscillation
frequency (fmax) were 20.1 and 47.6 GHz, and the
output power density and the power added efficiency
(PAE) at the peak PAE, at 20 V drain voltage and 3.5
GHz frequency were 3.83 W/mm and 57.2%,
respectively.
A 23‐31 GHz gallium nitride high‐robustness
low‐noise amplifier with 1.1‐dB noise figure and
28‐dBm saturation output power Microsystem and Terahertz Research Center, China
Academy ofEngineering Physics, Chengdu, China
Institute of Electronic Engineering, China Academy of
EngineeringPhysics, Mianyang, China
Microwave and Optical Technology Letters
https://doi.org/10.1002/mop.32130
A 23 to 31 GHz low‐noise amplifier (LNA) based on
0.1‐μm gallium nitride (GaN) on silicon (Si) microwave
monolithic integrated circuit process is presented in
this work. Three‐stage cascade topology was used in
the LNA design with chip area of 1.9 × 0.8 mm2. The
measured linear gain is 22 to 27 dB with low input
and output return loss. The noise figure (NF) was
measured with cold source methodology, which is
0.93 to 1.36 dB across the working frequency band.
The power characteristics were measured, which
indicate that this LNA has 1‐dB compression point
output power (P1dB) of 23 dBm and saturated output
power (Psat) of 28 dBm. The measured
output‐referred third‐order intercept point (OIP3)
was at 34 dBm level, which indicates the high
linearity of this LNA. To inspect the robustness,
30 dBm continuous wave input power was injected
into the working LNA for 5 minutes, no obvious
degradation was found after stress. Compared with
the traditional gallium arsenide (GaAs) and indium
phosphide (InP) LNA, GaN LNA reported in this work
has comparable NF but much higher robustness.
Moreover, this LNA has very high linearity, which
increases the immunity to jamming signal, enables
more complicated modulation mode and improves
data throughput. As we know, there is no GaN LNA
achieving such high P1dB and Psat with NF below 1.4
dB at this frequency band. This GaN LNA has a great
potential in the applications of electronic war,
anti‐electromagnetic interference and signal
detection.
Enhancement of Johnson figure of merit in III‐V
HEMT combined with discrete field plate and AlGaN
blocking layer Department of Electronics andCommunication
Engineering, KarunyaInstitute of Technology and
Sciences,Coimbatore, Tamilnadu, India
Department of Electronics andCommunication
Engineering, SNSCollege of Technology,
Coimbatore,Tamilnadu, India
Department of Electronics andCommunication, Malaviya
NationalInstitute of Technology, Jaipur, Rajasthan,India
International Journal of RF and Microwave Computer-
Aided Engineering
https://doi.org/10.1002/mmce.22040
The performance of AlGaN/GaN HEMT is enhanced
by using discrete field plate (DFP) and AlGaN blocking
layer. The AlGaN blocking layer provides an excellent
confinement of electrons toward the GaN channel,
resulting very low subthreshold drain current of 10−8
A/mm. It reveals very high off state breakdown
voltage (BV) of 342 V for 250 nm gate technology
HEMT. The breakdown voltage achieved for the
proposed HEMT is 23% higher when compared to the
breakdown voltage of conventional field plate HEMT
device. In addition, the DFP reduces the gate
capacitance (CG) from 12.04 × 10−13 to
10.48 × 10−13 F/mm. Furthermore, the drain current
and transconductance (gm) reported for the
proposed HEMT device are 0.82 A/mm and 314
mS/mm, respectively. Besides, the cut‐off frequency
(fT) exhibited for the proposed HEMT is 28 GHz.
Moreover, the proposed HEMT records the highest
Johnson figure of merit (JFOM) of 9.57 THz‐V for
250 nm gate technology without incorporating
T‐gate.
GaNEX | III-N Technology Newsletter No. 83 | 29
Impact of the in-situ SiN Thickness on Low-
Frequency Noise in MOVPE InAlGaN/GaN HEMTs Normandie Univ., UNICAEN, ENSICAEN, CNRS, GREYC,
14000 Caen, France. He is now with the DEI, University of
Padova, 35122 Padua, Italy
III-V Lab, Thales Research and Technology, 91767
Palaiseau, France
IEMN, 59650 Villeneuve d'Ascq, France
IEEE Transactions on Electron Devices
https://doi.org/10.1109/TED.2019.2945296
This article reports on sub-10-nm quaternary barrier
InAlGaN/GaN high electron mobility transistors
(HEMTs) grown by metal-organic-vapor-phase-
epitaxy (MOVPE) with an in situ SiN passivation layer
and an ultrashort gate length of 200 nm. Two batches
of HEMTs with two SiN thicknesses (tSiN) of 14 and
22 nm are studied. Low-frequency noise (LFN)
measurements of the drain current have been carried
out in the linear regime and showed that the in situ
SiN thickness has no impact on the noise
performance. SID/ID² in the linear regime
dependence over the gate overdrive shows that the
channel noise is located under the gate and that the
noise is not impacted by the thickness of the in situ
SiN layer.
Computer‐aided design methodology for linearity
enhancement of multiwatt GaN HEMT amplifiers
using multiple parallel devices Bradley Department of Electrical andComputer
Engineering, Virginia Tech,Arlington, Virginia
AMCOM Communications, Inc.,Gaithersburg, Maryland
University of Massachusetts, Amherst,Massachusetts
International Journal of RF and Microwave Computer-
Aided Engineering
https://doi.org/10.1002/mmce.22010
This article presents a design methodology for
linearizing GaN HEMT amplifiers based on splitting a
large FET into multiple parallel FETs with same total
gate periphery and by biasing them individually. By
varying the biases, the magnitude and the phase of
the IMD3 components at the output of FET changes.
A detailed simulation methodology using commercial
microwave CAD software is presented. Simulation
results show that by biasing one device in Class AB
and other(s) in deep Class AB mode, IMD3
components of parallel FETs can be made out of
phase to each other leading to cancellation and
improvement in linearity. Three prototype circuits
were simulated using (a) a single 5 mm FET
(1 × 5 mm), (b) two parallel 2.5 mm FETs (2 × 2.5 mm),
and (c) four parallel 1.25 mm FETs (4 × 1.25 mm), for
a total gate periphery of 5 mm, over the frequency
range of 0.8 to 1.0 GHz. IMD3 improvement up to
20 dBc was achieved with the 4 × 1.25 mm circuit
when the FET biases were optimized. Measurement
results show improvement in linearity up to 20 dBc
for 4 × 1.25 mm circuit. The proposed method
improves linearity without a substantial penalty on
the power consumption and is straightforward to
implement.
Sensitivity analysis for an electron transport system:
application to the case of wurtzite gallium nitride Mathematics, and Computer Science and Engineering,
University of North Texas, Denton, USA
Department of Mathematics, New Mexico Tech, Socorro,
USA
School of Engineering, The University of British Columbia,
Kelowna, Canada
Electrical, Computer, and Systems Engineering and Physics,
Applied Physics, and Astronomy, Rensselaer Polytechnic
Institute, Troy, USA
School of Computing and Scientific Computing and Imaging
Institute, University of Utah, Salt Lake City, USA
Journal of Computational Electronics
https://doi.org/10.1007/s10825-019-01424-1
Monte Carlo simulations, which are widely used for
predicting the transport properties of
semiconductors, use a large number of parameters,
such as the effective masses, the non-parabolic
constants, the deformation potential, the phonon
energies, and the elastic constants. Most of these
parameters are not very well known or have different
reported computed or measured values. In this
paper, we employ an uncertainty quantification
technique that allows us to determine the effect of
the uncertainty of parameter values on the transport
properties computed using the Monte Carlo
technique and establish the key parameters that
strongly affect the results in contrast to the
parameters whose wide variation has a small overall
impact.
GaNEX | III-N Technology Newsletter No. 83 | 30
Comparative Study of Variations in Gate Oxide
Material of a Novel Underlap DG MOS-HEMT for
Analog/RF and High Power Applications Electronics and Communication Engineering, Heritage
Institute of Technology, Kolkata, India
Silicon
https://doi.org/10.1007/s12633-019-00316-0
In this paper an Underlap Double Gate (U-DG)
Symmetric Heterojunction AlGaN/GaN Metal Oxide
Semiconductor High Electron Mobility Transistor
(MOS-HEMT) with gate oxide materials of different
dielectric constant has been studied using gate oxide
materials such as Hafnium dioxide (HfO2), Silicon
dioxide (SiO2) and a symmetric gate stack (GS) of
HfO2-SiO2. In this work, the analog performance of
the devices has been studied on the basis of
parameters like transconductance (gm),
transconductance generation factor (gm/ID) and
intrinsic gain (gmR0). This paper depicts the effect of
varying oxide materials on the analog and RF figure of
merits (FOMs) such as the gate to drain capacitance
(CGD), gate to source capacitance (CGS) and total
gate capacitance (CGG), intrinsic resistances, cut-off
frequency (fT) and maximum frequency of oscillation
(fMAX) using non-quasi-static approach. Studies show
that the introduction of a gate oxide layer in the
MOS-HEMT device increases the gate controllability
reducing gate leakage currents improving RF
performance. U-DG AlGaN/GaN MOS-HEMT with
HfO2 gate dielectric shows superior Power output
efficiency (POE) of 55% compared to the HfO2-SiO2
composite structure and SiO2 with 26% and 20%
respectively.
A Study on the First‐Derivative Output Properties of
GaN Static Induction Transistor with Submicrometer
Fin Width Department of Electrical Engineering, Stanford University,
Stanford, CA 94305, USA
Department of Electrical and Computer Engineering,
University of California, Davis, CA 95616, USA
physica status solidi b
https://doi.org/10.1002/pssb.201900545
The first derivative of output curves of a
Schottky‐junction vertical channel GaN static
induction transistor (SIT) with a submicrometer‐sized
fin is studied to understand its fundamental electrical
properties. It is found that the derivative of output
curves increases with the increase in drain voltage
(Vds) in ohmic region because of the raised potential
minima in the channel, which is not seen in SITs with
a relatively long fin width. The influence of the gate
voltages (Vgs) and Vds on electric potential in the
channel is demonstrated by evaluating the
contribution of Vgs and Vds, expressed through two
coefficients α and β. The ratio of α to β increases up
to 31.1 from 16.3 with decrease in the fin width from
0.9 to 0.5 μm, showing a higher dependency of the
potential minima on Vgs and the fin width. The
voltage gain expressed by α/β is 14.9 dB for the GaN
SIT with a fin width of 0.5 μm.
GaNEX | III-N Technology Newsletter No. 83 | 31
GROUP 5 – MEMS and Sensors Group leader: Marc Faucher (IEMN) Information selected by Knowmade
Fabrication of AlN/GaN MSM photodetector with
platinum as schottky contacts Department of Applied Sciences Universiti Teknologi
MARA, Cawangan Pulau Pinang 13500 Permatang Pauh,
Penang, Malaysia
Universiti Kuala Lumpur, Malaysian Institute of Industrial
Technology (MITEC), Persiaran Sinaran Ilmu, Bandar Seri
Alam, 81750 Johor, Malaysia
Institute of Nano-Optoelectronics Research and
Technology Universiti Sains Malaysia, 11800 Penang,
Malaysia
Materials Research Express
https://doi.org/10.1088/2053-1591/ab4a40
The epitaxial aluminium nitride (AlN) layer was
fabricated on a silicon (111) substrate by solid phase
radio frequency (RF) MBE The samples morphological
characteristic was successfully studied by field
emission SEM. Low photo-response of the hetero-
structure layers is one of the main obstacles in order
to fabricate a high performance of photodetector
device. The platinum contacts on AlN/GaN metal-
semiconductor-metal (MSM) photodetector were
formed by RF sputtering machine. The conductivity
behaviours, Schottky barrier height (SBH), photo-
responses of the device were examined by source
meter measurement. The SBH values of photo-device
sensing were calculated as 0.488 eV and 0.479 eV for
dark current and photo current, respectively. Good
response times of the device were recorded as 21.48
ms and 12.69 ms for the bias voltage of 1 volt.
Static and dynamic simulation studies on the
AlGaN/GaN pressure sensor School of Information Science and Engineering, Chengdu
University, Chengdu 610106, People's Republic of China
School of Mechanical Engineering, Southwest Jiaotong
University, Chengdu 610031, People's Republic of China
Semiconductor Science and Technology
https://doi.org/10.1088/1361-6641/ab478a
In this paper, electro-thermo-mechanical coupled
static and dynamic FEM simulations are adopted to
study the AlGaN/GaN pressure sensor. The sensor
sensitivity is expressed as the drain current change of
transistor integrated on the AlGaN/GaN cantilever or
circular diaphragm with the applied pressure, namely
piezoresistive effect, which is caused essentially by
the change of piezoelectric polarization charge. In the
static simulation study, how the transistor self-
heating, gate metal layer, AlGaN donor-like surface
states, and bulk acceptor-like traps in GaN influence
the sensitivity are separately illustrated. In the
dynamic simulation study, transient behavior of the
sensor with the bulk acceptor-like traps and
dependences of the natural frequency of circular
diaphragm on the self-heating as well as the position
of transistor integrated on the diaphragm are
analyzed. This work would provide useful guidelines
for the design and optimization of AlGaN/GaN
pressure sensor.
On-diaphragm Thermistor for High-temperature
Dynamic Pressure Sensors University of Texas at Austin, Austin, TX 78758 USA
Silicon Audio, Inc., Austin, TX 78702 USA
IEEE Sensors Journal
https://doi.org/10.1109/JSEN.2019.2953397
This article presents the fabrication and
characterization of on-diaphragm Pt thermistors for
temperaturecompensated calibration of piezoelectric
pressure sensors. The micromachined pressure-
sensitive diaphragms are 700 µm in diameter and
employ AlN as the piezoelectric material. The
thermistors reside on top of the diaphragms and are
patterned into a 100-nm-thick sputtered Pt electrode
layer. Experimental characterization up to 600 °C
demonstrates the importance of annealing to realize
hysteresis-free resistance vs. temperature
characteristics. Dynamic frequency response
measurements of the pressure-sensitive diaphragms
vs. temperature demonstrate a marked shift in
compliance with temperature, and therefore
demonstrates the importance of temperature-
GaNEX | III-N Technology Newsletter No. 83 | 32
compensated pressure calibration in high-
temperature measurement environments.
TCAD model for TeraFET detectors operating in a
large dynamic range Electrical, Computer and Systems Engineering, Rensselaer
Polytechnic Institute, 8024 Troy, New York United States
IEEE Transactions on Terahertz Science and Technology
https://doi.org/10.1109/TTHZ.2019.2952248
Technology computer-aided design (TCAD) models
for AlGaAs/InGaAs and AlGaN/GaN and silicon SOI
TeraFETs are in good agreement with the measured
current-voltage characteristics and the response to
the sub-THz radiation. They allowed us to establish
the physical mechanism of the observed response
saturation at high intensities, not reproduced by the
analytical model. By activating or deactivating
different physical mechanisms in the TCAD models,
we show that the response saturation is caused by
the gate leakage for AlGaAs/InGaAs HFETs and
AlGaN/GaN HFETs and by the avalanche effect for Si
SOI MOSFETs.
Converse Magnetoelectric Composite Resonator for
Sensing Small Magnetic Fields Institute for Materials Science, Kiel University, Kiel, 24143,
Germany
Institute of Electrical and Information Engineering, Kiel
University, Kiel, 24143, Germany
MIREA - Russian Technological University, Moscow,
119454, Russia
IFW Dresden, SAWLab Saxony, Dresden, 01171, Germany
Scientific Reports
https://doi.org/10.1038/s41598-019-52657-w
Magnetoelectric (ME) thin film composites consisting
of sputtered piezoelectric (PE) and magnetostrictive
(MS) layers enable for measurements of magnetic
fields passively, i.e. an AC magnetic field directly
generates an ME voltage by mechanical coupling of
the MS deformation to the PE phase. In order to
achieve high field sensitivities a magnetic bias field is
necessary to operate at the maximum piezomagnetic
coefficient of the MS phase, harnessing mechanical
resonances further enhances this direct ME effect
size. Despite being able to detect very small AC field
amplitudes, exploiting mechanical resonances
directly, implies a limitation to available signal
bandwidth along with the inherent inability to detect
DC or very low frequency magnetic fields. The
presented work demonstrates converse ME
modulation of thin film Si cantilever composites of
mesoscopic dimensions
(25 mm × 2.45 mm × 0.35 mm), employing
piezoelectric AlN and magnetostrictive FeCoSiB films
of 2 µm thickness each. A high frequency mechanical
resonance at about 515 kHz leads to strong induced
voltages in a surrounding pickup coil with matched
self-resonance, leading to field sensitivities up to
64 kV/T. A DC limit of detection of 210 pT/Hz1/2 as
well as about 70 pT/Hz1/2 at 10 Hz, without the need
for a magnetic bias field, pave the way towards
biomagnetic applications.
Study of a GaN Schottky diode-based hydrogen
sensor with a hydrogen peroxide oxidation
approach and platinum catalytic metal Department of Chemical Engineering, National Cheng Kung
University, Tainan, 70101, Taiwan, Republic of China
Institute of Microelectronics, Department of Electrical
Engineering, National Cheng Kung University, Tainan,
70101, Taiwan, Republic of China
Department of Computer Science and Information
Engineering, Chaoyang University of Technology, Taichung,
41349, Taiwan, Republic of China
International Journal of Hydrogen Energy
https://doi.org/10.1016/j.ijhydene.2019.10.112
A platinum (Pt) catalytic metal and a hydrogen
peroxide oxidation approach are utilized to fabricate
a hydrogen sensor based on a GaN Schottky diode.
The presence of a gallium oxide dielectric layer
between the Pt metal and the GaN surface can
increase the adsorption sites for dissociated
hydrogen species, thereby improving the related
sensing ability towards hydrogen gas. Experimentally,
under introduced 1% hydrogen/air gas, the studied
device shows a high sensing response ratio of 1.03 ×
105 at 300 K. In addition, the lowest detecting level
of 1 ppm hydrogen at 300 K is obtained. This device
also exhibits good high-temperature durability (≥573
K) and a high sensing speed. The response (recovery)
time constant at 300 K is only 74 (103) sec even
under a very low hydrogen concentration of 1 ppm;
these time constant values are much smaller than
GaNEX | III-N Technology Newsletter No. 83 | 33
those of palladium metal-based sensors. Under the
1% hydrogen/air, the response (recovery) time
constant at 300 K is drastically reduced to 15 (19) sec.
Furthermore, in order to improve the feasibility of
transmitting the sensing data, the concept of linear
differentiation method is employed to eliminate
redundant data. The simulation result shows that the
average of the reduced ratios can achieve 77.88%.
Therefore, this Schottky diode device not only shows
promise to detect hydrogen gas, but also can be
utilized effectively in the transmission of sensing
data.
Seeing pressure in color based on integration of
highly sensitive pressure sensor and emission
tunable light emitting diode Graduate Institute of Applied Physics, National Taiwan
University, Taipei 10617, Taiwan
Department of Physics, National Taiwan University, Taipei
10617, Taiwan
Department of Electro-physics, National Chiao Tung
University, Hsinchu 30010, Taiwan
Department of Materials Science and Engineering, National
Tsing Hua University, Hsinchu 30013, Taiwan
Department of Photonics and Institute of Electro-optical
Engineering, National Chiao Tung University, Hsinchu
30010, Taiwan
Department of Chemical Engineering and Biotechnology,
National Taipei University of Technology, Taipei 10617,
Taiwan
Department of Physics, National Sun Yat-sen University,
Kaohsiung 80424, Taiwan
Optics Express
https://doi.org/10.1364/OE.27.035448
We demonstrate a highly sensitive, low-cost,
environmental-friendly pressure sensor derived from
a wool-based pressure sensor with wide pressure
sensing range using wool bricks embedded with a Ag
nano-wires. The easy fabrication and light weight
allow portable and wearable device applications. Wth
the integration of a light-emitting diode possessing
multi-wavelength emission, we illustrate a hybrid
multi-functional LED-integrated pressure sensor that
is able to convert different applied pressures to light
emission with different wavelengths. Due to the high
sensitivity of the pressure sensor, the demonstration
of acoustic signal detection has also been presented
using sound of a metronome and a speaker playing a
song. This multi-functional pressure sensor can be
implemented to technologies such as smart lighting,
health care, visible light communication (VLC), and
other internet of things (IoT) applications.
Fabrication and characterization of AlN-based
flexible piezoelectric pressure sensor integrated into
an implantable artificial pancreas CNR-IMM Institute for Microelectronics and Microsystems,
Via Monteroni, 73100, Lecce, Italy
BioRobotics Institute and Department of Excellence in
Robotics & AI, Scuola Superiore Sant’Anna, 56025,
Pontedera, Italy
Scientific Reports
https://doi.org/10.1038/s41598-019-53713-1
This study reports on the fabrication and
characterization of an event detection subsystem
composed of a flexible piezoelectric pressure sensor
and the electronic interface to be integrated into an
implantable artificial pancreas (IAP) for diabetic
patients. The developed sensor is made of an AlN
layer, sandwiched between two Ti electrodes,
sputtered on Kapton substrate, with a preferential
orientation along c-axis which guarantees the best
piezoelectric response. The IAP is made of an
intestinal wall-interfaced refilling module, able to
dock an ingestible insulin capsule. A linearly actuated
needle punches the duodenum tissue and then the
PDMS capsule to transfer the insulin to an implanted
reservoir. The device is located at the connection of
the needle with the linear actuator to reliably detect
the occurred punching of the insulin-filled capsule.
Finite Element Analysis (FEA) simulations were
performed to evaluate the piezoelectric charge
generated for increasing loads in the range of
interest, applied on both the sensor full-area and
footprint area of the Hamilton needle used for the
capsule punching. The sensor-interface circuit was
simulated to estimate the output voltage that can be
obtained in real operating conditions. The
characterization results confirmed a high device
sensitivity during the punching, in the low forces (0–
4 N) and low actuator speed (2–3 mm/s) ranges of
interest, meeting the requirement of the research
objective. The choice of a piezoelectric pressure
sensor is particularly strategic in the medical field due
to the request of self-powered implantable devices
GaNEX | III-N Technology Newsletter No. 83 | 34
which do not need any external power source to
output a signal and harvest energy from natural
sources around the patient.
Neutron detection performance of gallium nitride-
based semiconductors Department of Electrical and Computer Engineering,
Missouri University of Science and Technology, Missouri,
65409, USA
Department of Electrical and Computer Engineering,
University of North Carolina at Charlotte, Charlotte, North
Carolina, 28223, USA
Nuclear Engineering Program, Idaho State University,
Pocatello, Idaho, 83209, USA
Nuclear Engineering Program, Georgia Institute of
Technology, Atlanta, Georgia, 30332, USA
Southern Polytechnic College of Engineering and
Engineering Technology, Kennesaw State University,
Marietta, GA, 30060, USA
Scientific Reports
https://doi.org/10.1038/s41598-019-53664-7
Neutron detection is crucial for particle physics
experiments, nuclear power, space and international
security. Solid state neutron detectors are of great
interest due to their superior mechanical robustness,
smaller size and lower voltage operation compared to
gas detectors. Gallium nitride (GaN), a mature wide
bandgap optoelectronic and electronic
semiconductor, is attracting research interest for
neutron detection due to its radiation hardness and
thermal stability. This work investigated thermal
neutron scintillation detectors composed of GaN thin
films with and without conversion layers or rare-
earth doping. Intrinsic GaN-based neutron
scintillators are demonstrated via the intrinsic 14N(n,
p) reaction, which has a small thermal neutron cross-
section at low neutron energies, but is comparable to
other reactions at high neutron energies (>1 MeV).
Gamma discrimination is shown to be possible with
pulse-height in intrinsic GaN-based scintillation
detectors. Additionally, GaN-based scintillation
detector with a 6LiF neutron conversion layer and
Gd-doped GaN detector are compared with intrinsic
GaN detectors. These results indicate GaN scintillator
is a suitable candidate neutron detector in high-flux
applications.
Suspended tungsten trioxide (WO3) gate
AlGaN/GaN heterostructure deep ultraviolet
detectors with integrated micro-heater Department of Microelectronics, Delft University of
Technology, 2628 CD Delft, Netherlands
Research and Development Center for Solid State Lighting,
Institute of Semiconductors, Chinese Academy of Sciences,
Qinghua East Road 35A, 100083, Beijing, China
State Key Laboratory of Solid State Lighting, Beijing,
100083, China
Institute of Microelectronic, Tsinghua University 100084,
Beijing, China
Optics Express
https://doi.org/10.1364/OE.27.036405
A suspended WO3-gate AlGaN/GaN heterostructure
photodetector integrated with a micro-heater is
micro-fabricated and characterized for ultraviolet
photo detection. The transient optical characteristics
of the photodetector at different temperatures are
studied. The 2DEG-based photodetector shows a
recovery (170 s) time under 240 nm illumination at
150 ℃. The measured spectral response of WO3-gate
AlGaN/GaN heterostructure shows a high response in
deep ultraviolet range. Responsivity at 240 nm
wavelength is 4600 A/W at 0.5 V bias. These
characteristics support the feasibility of a high
accuracy deep UV detector based on the suspended
AlGaN/GaN heterostructure integrated with a micro-
heater.
Ultrafast pyroelectric photodetection with on-chip
spectral filters Department of Electrical and Computer Engineering, Duke
University, Durham, NC, USA
Sensors Directorate, Air Force Research Laboratory,
Wright–Patterson Air Force Base, Dayton, OH, USA
Ginzton Laboratory, Department of Electrical Engineering,
Stanford University, Stanford, CA, USA
Department of Physics, Duke University, Durham, NC, USA
Nature Materials
https://doi.org/10.1038/s41563-019-0538-6
Thermal detectors, such as bolometric, pyroelectric
and thermoelectric devices, are uniquely capable of
sensing incident radiation for any electromagnetic
frequency; however, the response times of practical
devices are typically on the millisecond
GaNEX | III-N Technology Newsletter No. 83 | 35
scale1,2,3,4,5,6,7. By integrating a plasmonic
metasurface with an aluminium nitride pyroelectric
thin film, we demonstrate spectrally selective, room-
temperature pyroelectric detectors from 660–
2,000 nm with an instrument-limited 1.7 ns full width
at half maximum and 700 ps rise time. Heat
generated from light absorption diffuses through the
subwavelength absorber into the pyroelectric film
producing responsivities up to 0.18 V W−1 due to the
temperature-dependent spontaneous polarization of
the pyroelectric films. Moreover, finite-element
simulations reveal the possibility of reaching a 25 ps
full width at half maximum and 6 ps rise time rivalling
that of semiconductor photodiodes8. This design
approach has the potential to realize large-area,
inexpensive gigahertz pyroelectric detectors for
wavelength-specific detection from the ultraviolet to
short-wave infrared or beyond for, for example, high-
speed hyperspectral imaging.
Low Voltage High-Energy α-Particle Detectors by
GaN-on-GaN Schottky Diodes with Record-High
Charge Collection Efficiency School of Electrical and Electronics Engineering, Nanyang
Technological University, Singapore 639798, Singapore
Temasek Laboratories @ NTU, Research Techno Plaza, 50
Nanyang Drive, Singapore 639798, Singapore
Center for Integrated Research of Future Electronics
(CIRFE), IMaSS, Nagoya University, Nagoya 464-8603,
Japan
National Isotope Center, GNS Science, Lower Hutt 5010,
New Zealand
Sensors
https://doi.org/10.3390/s19235107
A low voltage (−20 V) operating high-energy (5.48
MeV) α-particle detector with a high charge
collection efficiency (CCE) of approximately 65% was
observed from the compensated (7.7 × 1014 /cm3)
metalorganic vapor phase epitaxy (MOVPE) grown 15
µm thick drift layer gallium nitride (GaN) Schottky
diodes on free-standing n+-GaN substrate. The
observed CCE was 30% higher than the bulk GaN (400
µm)-based Schottky barrier diodes (SBD) at −20 V.
This is the first report of α–particle detection at 5.48
MeV with a high CCE at −20 V operation. In addition,
the detectors also exhibited a three-times smaller
variation in CCE (0.12 %/V) with a change in bias
conditions from −120 V to −20 V. The dramatic
reduction in CCE variation with voltage and improved
CCE was a result of the reduced charge carrier density
(CCD) due to the compensation by Mg in the grown
drift layer (DL), which resulted in the increased
depletion width (DW) of the fabricated GaN SBDs.
The SBDs also reached a CCE of approximately 96.7%
at −300 V.
GaNEX | III-N Technology Newsletter No. 83 | 36
GROUP 6 - Photovoltaics and Energy harvesting Group leader: Eva Monroy (INAC-CEA)
Information selected by Knowmade
Improved ability of artificial photosynthesis by using
InGaN/AlGaN/GaN electrode Key Lab. for New Type of Functional Materials in Hebei
Province, School of Materials Science and Engineering,
Hebei University of Technology, Tianjin 300132, People's
Republic of China
School of Electronic Engineering, Tianjin University of
Technology and Education, Tianjin 300222, People's
Republic of China
Applied Physics Express
https://doi.org/10.7567/1882-0786/ab495c
We have successfully demonstrated the enhanced
capability of CO2 conversion using InGaN/AlGaN/GaN
photoelectrode. The CO2 conversion ability of the
system is improved due to the improvement of the
cathode potential by changing the light absorbing
layer which effectively combines the piezoelectric
polarization effect of the AlGaN/GaN structure and
the high absorption for light by InGaN. Our results
suggest that the photocurrent is increased by two
times than that produced by AlGaN/GaN.
Furthermore, the ability of convert to CO is
enhanced. Aside from H2 and CO, the concentration
of hydrocarbons is also improved.
A new lattice-matched In0.17Al0.83N ~ GaN based
heterostructure IMPATT diode for terahertz
application State Key Discipline Laboratory of Wide Bandgap
Semiconductor Technology, School of Microelectronics,
Xidian University, Xi'an 710071, People's Republic of China
Weifang University, Weifang 261061, People's Republic of
China
Semiconductor Science and Technology
https://doi.org/10.1088/1361-6641/ab4786
Simulation studies are made on the dc and
microwave performance of a novel lattice-matched
In0.17Al0.83N/GaN heterostructure impact
avalanche transit time (IMPATT) diode designed at
the low-end terahertz frequency of 220 GHz. The
electric field, breakdown voltage, rf output power
and the dc-to-rf conversion efficiency of the
heterostructure IMPATT diodes are compared with
the GaN homostructure IMPATT diode. The results
show that, a more localized avalanche region width is
obtained for the heterostructure IMPATT diodes.
With value of 45 nm of the In0.17Al0.83N layer
width, the heterostructure IMPATT diode gives the
highest efficiency (15.4%) with moderate rf output
power density (1.62 MW cm−2), and the lowest Q-
factor (6.57) as compared to other heterostructure
and homostructure IMPATT diodes.
Development of InxGa1-xN/GaN Axial Multiple
Quantum Well Nanowire for Solar Cell Applications Faculty of Technology University of Blida.1, 09000, Blida,
Algeria
Institut d’Electronique, de Microe´lectronique et de
Nanotechnologie (IEMN), UMR CNRS 8520, Universite´ des
Sciences et Technologies de Lille 1, Avenue Poincare´, BP
60069, 59652, Villeneuve d’Ascq, France
Optik
https://doi.org/10.1016/j.ijleo.2019.163844
In this paper, we report a simulation and
investigation of a single InxGa1-xN/GaN axial multiple
quantum well nanowire (MQWNW) solar cell of
radius r = 190 nm and a length of L = 1165 nm. Our
results have been shown that 15 In0.15Ga0.85N
(QW) /GaN (barrier) periods is the maximum number
that our structure can be supported with an optimal
efficiency of about 1.65% achieved with ε = 1.5%. The
insertion of MQWs in nanowire permits the growth of
InxGa1-xN MQWs with high indium concentration of
about 50% and ε = 5%. At this indium concentration,
the optimal efficiency obtained was 1.70%.
Moreover; the structure has been studied with
respect to the nanowire radius. In this context, we
have shown that the efficiency enhancement
achieved through the increase of radius is attributed
to the increase of photo-carriers. Study of
polarization and proton irradiations has indicated the
negative effect of polarization on structure
GaNEX | III-N Technology Newsletter No. 83 | 37
performances and high resistance of III-N
semiconductor materials against the radiations,
respectively. From these novel structures we can
improve solar cell performance for new applications.
Boosting photoelectrochemical performance of GaN
nanowall network photoanode with
bacteriorhodopsin Central Scientific Instruments Organization, Sector-30C,
Chandigarh, 160030, India
AcSIR, Council of Scientific and Industrial Research,
Ghaziabad, 201002, India
School of Materials Science, Indian Association for the
Cultivation of Science, Kolkata, 700032, India
Institute of Microbial Technology, Sector 39A, Chandigarh,
160036, India
Jawaharlal Nehru Centre for Advanced Scientific Research,
Bangalore, 560064, India
International Journal of Hydrogen Energy
https://doi.org/10.1016/j.ijhydene.2019.10.184
The ever-increasing demand for renewable and clean
energy sources has prompted the development of
novel materials for photoelectrochemical (PEC) water
splitting, but efficient solar to hydrogen conversion
remains a big challenge. In this work, we report a bio-
nanohybrid strategy in a photo-system to
simultaneously enhance the charge separation and
water splitting efficiency of photoanode (PA) by
introducing Bacteriorhodopsin (bR), a natural proton
pumping photosystem and GaN nanowall network
(NWN), a direct band gap and corrosion-resistant
semiconductor. The experimental study reveals that
this combination of bR and GaN NWN has huge
potential as a light-activated sensitizer as well as
proton pumping source to achieve enhance
photocurrent density in hydrogen evolution reaction
(HER). Consequently, this synergistic effect in bR/GaN
NWN PA gives rise to largely enhanced applied bias
photon-to-current efficiency (ABPE) ~7.8% and
photocurrent density (28.74 mA/cm2 at 1.0 V vs
RHE). It is worth mentioning that the photocurrent
density of bR/GaN NWN, to the best of our
knowledge, is superior to previously reported bR-
based PAs and bio-photoelectric devices reported till
today for solar-to-hydrogen fuel generation.
Rotation Tunable Photocatalytic Properties of
ZnO/GaN Heterostructures School of Electronic Information Engineering, Key
Laboratory of Extraordinary Bond Engineering and
Advanced Materials Technology of Chongqing, Yangtze
Normal University, Chongqing 408100, China
School of Physical Science and Technology, Southwest
University, Chongqing 400715, China
Department of Physics, Chongqing University of Arts and
Sciences, Chongqing 402160, China
physica status solidi b
https://doi.org/10.1002/pssb.201900663
Using hybrid density functional calculations, we
explore how rotation angles can influence the
photocatalytic performance of two‐dimensional (2D)
ZnO/GaN heterostructures. Our results show that the
bandgaps and band alignments for ZnO/GaN
heterostructures can be tuned by rotation angles.
Rotated ZnO/GaN heterostructures are favorable for
visible light absorption. Band alignments of different
rotated ZnO/GaN heterostructures are severally
thermodynamically favorable for spontaneous
generation of hydrogen and oxygen with the pH
scope of 0‐14, 3‐14, 2‐14, 1‐14, 1‐14, and 4‐14.
Besides, the formed built‐in electric field across
ZnO/GaN heterostructure interface promotes
photogenerated carrier migration and inhibits
photogenerated carrier recombination. These factors
make rotated ZnO/GaN heterostructures promising
for visible light water‐splitting. Our findings pay a
new way to design 2D heterostructures used for
photocatalytic water‐splitting.
Surface Electronic Properties of Si‐Doped AlGaN and
Thermionic Emission Characteristics with Adsorption
of Alkali Metal Atoms Corporate Research and Development Center, Toshiba
Corporation 1, Komukai-toshiba-cho, Saiwai-ku, Kawasaki,
Kanagawa, 212-8584, Japan
physica status solidi a
https://doi.org/10.1002/pssa.201900719
A thermionic energy converter (TEC) is a heat engine
with a high theoretical efficiency, but a reduction in
operating temperature is required for practical
applications. Herein, the experimentally determined
thermionic conversion characteristics of Si‐doped
GaNEX | III-N Technology Newsletter No. 83 | 38
GaN films with Cs adsorption at 600 °C are reported.
Low‐temperature thermionic emission around 300 °C
is also reported for Si‐doped AlGaN surfaces with Cs
adsorption. This emission temperature is
considerably lower than the operating temperatures
of conventional systems with a metal emitter. The
AlGaN thin films are grown on n‐type 6H‐SiC
substrates, and it is confirmed by ultraviolet
photoelectron spectroscopy that the work function
decreases as the AlN mole fraction x in the AlGaN
samples is increased. Threshold temperatures of
thermionic emission decrease with increasing AlN
mole fraction and a corresponding reduction in the
work function.
Two dimensional ZnO/AlN composites used for
photocatalytic water-splitting: a hybrid density
functional study School of Electronic Information Engineering, Key
Laboratory of Extraordinary Bond Engineering and
Advanced Materials Technology of Chongqing, Yangtze
Normal University, Chongqing 408100, China
School of Physical Science and Technology, Southwest
University, Chongqing 400715, China
Institute for Advanced Study, Nanchang University,
Nanchang 330031, China
RSC Advances
https://doi.org/10.1039/C9RA06104E
Using hybrid density functionals, we study the
interfacial interactions and electronic properties of
ZnO/AlN composites with the consideration of
rotation angles and biaxial strains in order to enhance
the photocatalytic performance for water-splitting.
The different rotated composites, and −2% strained,
original, and 2% strained ZnO/AlN composites can be
easily prepared owing to the negative interface
formation energies. The bandgaps and band
alignments of ZnO/AlN composites can be
significantly tuned by biaxial strains. Particularly, the
appropriate bandgap for visible light absorption,
proper band alignment for spontaneous water-
splitting, and the formed electric field promoting
photoinduced carrier separation make the 2%
strained ZnO/AlN composite a potential candidate for
photocatalytic water-splitting. This work shines some
light on designing two dimensional heterostructured
photocatalysts.
Long-Term Stability Studies of a Semiconductor
Photoelectrode Protected by Gallium Nitride
Nanostructures
Journal of Materials Chemistry A
https://doi.org/10.1039/C9TA09926C
Improving the stability of semiconductor materials is
one of the major challenges for sustainable and
economic photoelectrochemical water splitting. N-
terminated GaN nanostructures have emerged as a
practical protection layer for conventional high
efficiency but unstable Si and III-V photoelectrodes,
due to their near-perfect conduction band-alignment,
which enables efficient extraction of photo-
generated electrons, and N-terminated surfaces,
which protects against chemical and photo-corrosion.
Here, we demonstrate that Pt-decorated GaN
nanostructures on n+-p Si photocathode can exhibit
ultrahigh stability of 3000 h (i.e., over 500 days for
usable sunlight ~5.5 h per day) at a large
photocurrent density (> 35 mA/cm2) under AM 1.5G
one-sun illumination. The measured applied bias
photon-to-current efficiency of 11.9%, with an
excellent onset potential of ~ 0.56 V vs. RHE, is one of
the highest values reported for a Si photocathode
under AM 1.5G one-sun illumination. This study
provides a paradigm shift for the design and
development of semiconductor photoelectrodes for
PEC water splitting: stability is no longer limited by
the light absorber, but rather by co-catalyst particles.
Built-in magnetic-electrical coupling enhances
photocatalytic performance of GaN/ZnO: a first
principle study College of Materials Science and Engineering, Inner
Mongolia University of Technology, Hohhot 010051, PR
China
College of Physics, Mudanjiang Normal University,
Mudanjiang 157011, PR China
Inner Mongolia Key Laboratory of Thin Film and Coatings,
Hohhot 010051, PR China
Physica B: Condensed Matter
https://doi.org/10.1016/j.physb.2019.411902
The electronic structure and transfer characteristic of
holes and electrons of GaN/ZnO heterojunction polar
interface with cation vacancy were calculated by first-
GaNEX | III-N Technology Newsletter No. 83 | 39
principle. Results show that the defect levels induced
by VZn in Zn-N interface are made up of N-2p and O-
2p states. The degeneracy of the defect levels and
intrinsic CBM reduce the band gap of system.
However, the defect level formed by the O-2p state
may become a recombination center, which is not
conducive to the separation of holes and electrons. In
contrast, the defect level induced by VGa in the Ga-O
interface does not become a recombination center,
and the larger built-in electric polarization intensity in
the interface can effectively prevent the
recombination of holes and electrons. In addition, the
spin polarization of p states weakly bound electrons
induced by cation vacancy leads to spin-band-
splitting in the conduction band, which reduces the
effective mass of electron and increases the transfer
velocity difference between holes and electrons, so
that photogenerated holes and electrons can be
effectively separated.
GaNEX | III-N Technology Newsletter No. 83 | 40
GROUP 7 - Materials, Technology and Fundamental Group leader: Jean-Christophe Harmand (LPN-CNRS)
NANO
Information selected by Jesús Zúñiga Pérez (CRHEA-CNRS)
Effect of KOH passivation for top-down fabricated
InGaN nanowire light emitting diodes Department of Microsystems Engineering, Rochester
Institute of Technology, Rochester, New York 14623, USA
Department of Electrical and Microelectronic
Engineering, Rochester Institute of Technology,
Rochester, New York 14623, USA
Journal of Applied Physics
https://doi.org/10.1063/1.5123171
Gallium nitride (GaN) nanowire (NW) light emitting
diodes (LEDs) are promising candidates for
microdisplay applications due to smaller dimensions
and potential for novel integration approaches. For
the commonly adopted top-down GaN NW
fabrication, the required dry etching steps tend to
result in surface states, leading to reduced radiative
recombination rates in LEDs. To passivate the
surface and tune the diameter of the NWs,
hydroxyl-based chemicals such as potassium
hydroxide (KOH) are widely used to treat the
surface of these nanostructures. However, studies
on the effects of temperature, concentration, and
the damage recovery aspects of hydroxyl etching of
GaN NWs are very scarce. These etching
parameters are of great importance for device
performance. Here, these effects are explored
thoroughly with a focus on the correlation of
InGaN/GaN NW LED performances to KOH etching
temperature, concentration, and time, together
with a fundamental crystallographic analysis. The
KOH concentration resulting in total removal of the
NW base tapering and a collimated etch profile for
InGaN NW LEDs was found to be 0.8 wt. % at a
temperature of 45 °C. A 20 min etch at 23 °C with a
0.1 wt. % KOH concentration will remove surface
states from a top-down fabricated NW LED to
recover up to 90% of the peak photoluminescence
(PL) intensity lost by the dry etch step. The
oscillation behavior in PL intensity with regard to
the KOH etch time has been demonstrated in
InGaN/GaN NW LEDs for the first time, which will
shed light upon the design and passivation of these
devices for microdisplays.
Subliming GaN into ordered nanowire arrays for
ultraviolet and visible nanophotonics Nanophotonics Center, NTT Corp., 3-1, Morinosato
Wakamiya, Atsugi, Kanagawa 243-0198, Japan
NTT Basic Research Laboratories, NTT Corp., 3-1,
Morinosato Wakamiya, Atsugi, Kanagawa 243-0198,
Japan
Université Côte d’Azur, CNRS, CRHEA,Rue B. Grégory,
06560 Valbonne, France
NTT Device Technology Laboratory, NTT Corp., 3-1,
Morinosato Wakamiya, Atsugi, Kanagawa 243-0198,
Japan
ACS Photonics
https://doi.org/10.1021/acsphotonics.9b01435
We report on the fabrication of ordered arrays of
InGaN/GaN nanowire quantum disks by a top-down
selective-area sublimation method. Using a
combination of two-dimensional molecular beam
epitaxy of InGaN/GaN quantum wells, electron-
beam lithography and ultra-high-vacuum
sublimation techniques, we demonstrate that the
position, geometry and dimensions of nanowires
can be finely controlled at nano-, micro- and macro-
scales. Relying on a large set of structural data, we
evaluate in particular the relative sublimation rates
of GaN crystal planes that drive the nanowire
formation, we assess the intrinsic limits of selective
area sublimation for the fabrication of NW arrays
and we evaluate the homogeneity of the process
across the wafer. Because the sublimation method
preserves the crystal quality of the NW material, we
show that InGaN/GaN NWs present good optical
properties, which can be leveraged for photonic
applications in the ultraviolet and the visible range.
In particular, we demonstrate that it is possible to
realize on the same wafer not only arrays of
nanowires that individually support room-
temperature lasing based on Fabry-Pérot
resonances, but also subwavelength nanowires that
GaNEX | III-N Technology Newsletter No. 83 | 41
we integrate in photonic crystals for the realization
of nanowire-induced nanocavities.
Mg and In Codoped p-type AlN Nanowires for pn
Junction Realization IRIG-PHELIQS, NPSC, University Grenoble Alpes, CEA,
38000 Grenoble, France
Grenoble INP, Institut Néel, University Grenoble Alpes,
CNRS, 38000 Grenoble, France
Institute of Materials Science, Universidad de Valencia,
Valencia, Spain
NanoLetters
https://doi.org/10.1021/acs.nanolett.9b01394
Efficient, mercury-free deep ultraviolet (DUV) light-
emitting diodes (LEDs) are becoming a crucial
challenge for many applications such as water
purification. For decades, the poor p-type doping
and difficult current injection of Al-rich AlGaN-
based DUV LEDs have limited their efficiency and
therefore their use. We present here the significant
increase in AlN p-doping thanks to Mg/In codoping,
which leads to an order of magnitude higher Mg
solubility limit in AlN nanowires (NWs). Optimal
electrical activation of acceptor impurities has been
further achieved by electron irradiation, resulting in
tunnel conduction through the AlN NW p–n
junction. The proposed theoretical scenario to
account for enhanced Mg incorporation involves an
easy ionization of In-vacancy complex associated
with a negative charging of Mg in In vicinity. This
leads to favored incorporation of negatively
charged Mg into the AlN matrix, opening the path
to the realization of highly efficient NW-based LEDs
in the DUV range.
Atomistic Modeling of Fine Structure Splitting in
InGaN/GaN Dot-in-Nanowire Structures for Use in
Entangled Photon Pair Generation Department of Electrical and Computer Engi-neering,
Southern Illinois University Carbondale, IL 62901 USA
IEEE Journal of Quantum Electronics
https://doi.org/10.1109/JQE.2019.2955938
Fine structure splitting (FSS) is a bottleneck in
quantum dot (QD) based solid-state entangled
photon pair sources for application in quantum key
distribution (QKD). In QDs, entangle photon pairs
are generated through a cascaded emission
process: biexciton to exciton to the ground state.
The FSS of the excitonic states destroys the
entanglement of the photon pairs, hence needs to
be eliminated. For numerical in-vestigation of FSS
and design optimization, a multiscale-multiphysics
many-body calculation is required. In this work, we
report the coupling of full configuration interaction
(FCI) method with 10-band (sp3s*-spin) tight-
binding (TB) model to calculate the excitonic
energetics of realistically-sized InGaN/GaN dot-in-
nanowire structures. Model benchmarking has been
done against a recently-reported InGaN/GaN
multiple quantum well (MQW) structure in the a-
plane orientation. Computational methodology of
implementing hexagonal-base truncated pyramid
shaped QD has been presented. The effects of QD
shape/thickness, material composition, and crystal
growth direction (polar c-plane and non-polar m-
plane and a-plane) on the FSS of InGaN/GaN based
photon emitters have been investigated.
Polarization profiles of the emitted photons from
the excitonic transitions have been derived
quantum me-chanically from transition dipole
moments. With the smallest FSS, the non-polar m-
plane device has been found to be most promising
for the QKD application.
Exploring the potential of c-plane indium gallium
nitride quantum dots for twin-photon emission Tyndall National Institute, University College Cork, Cork
T12 R5CP, Ireland
Department of Electrical Engineering, University College
Cork, Cork T12 YN60, Ireland
NanoLetters
https://doi.org/10.1021/acs.nanolett.9b03740
Non-classical light emission, such as entangled and
single-photon emission, has attracted significant
interest due its importance for future quantum
technology applications. In this work, we study the
potential of wurtzite (In,Ga)N/GaN quantum dots
for novel non-classical light emission namely twin-
photon emission. Our calculations, based on a fully
atomistic many body framework, reveal that the
combination of carrier localization due to random
alloy fluctuations in the dot, spin-orbit coupling
effects, underlying wurtzite crystal structure and
GaNEX | III-N Technology Newsletter No. 83 | 42
built-in electric fields lead to an excitonic fine
structure that is very different from more
"conventional" zincblende (In,Ga)As dots, which
have been used so far for twin photon emission. We
show and discuss here that the four energetically
lowest exciton states are all bright and emit linearly
polarized light. Furthermore, three of these
excitonic states are basically degenerate. All these
results are independent of the alloy microstructure.
Also, our calculations reveal large exciton binding
energies (>35 meV), which exceed the thermal
energy at room temperature. Therefore,
(In,Ga)N/GaN dots are very promising candidates to
achieve efficient twin photon emission, potentially
at high temperatures and over a wide emission
wavelength range.
Displacement Talbot lithography for nano-
engineering of III-nitride materials Department of Electrical & Electronic Engineering,
University of Bath, Bath, BA2 7AY, UK
Université Côte d’Azur, CNRS, CRHEA, rue B. Gregory,
06560, Valbonne, France
Ferdinand-Braun-Institut, Leibniz-Institut für
Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489,
Berlin, Germany
Technische Universität Berlin, Institute of Solid State
Physics, 10623, Berlin, Germany
Microsystems & Nanoengineering
https://doi.org/10.1038/s41378-019-0101-2
Nano-engineering III-nitride semiconductors offers
a route to further control the optoelectronic
properties, enabling novel functionalities and
applications. Although a variety of lithography
techniques are currently employed to nano-
engineer these materials, the scalability and cost of
the fabrication process can be an obstacle for large-
scale manufacturing. In this paper, we report on the
use of a fast, robust and flexible emerging
patterning technique called Displacement Talbot
lithography (DTL), to successfully nano-engineer III-
nitride materials. DTL, along with its novel and
unique combination with a lateral planar
displacement (D2TL), allow the fabrication of a
variety of periodic nanopatterns with a broad range
of filling factors such as nanoholes, nanodots,
nanorings and nanolines; all these features being
achievable from one single mask. To illustrate the
enormous possibilities opened by DTL/D2TL,
dielectric and metal masks with a number of
nanopatterns have been generated, allowing for the
selective area growth of InGaN/GaN core-shell
nanorods, the top-down plasma etching of III-
nitride nanostructures, the top-down sublimation of
GaN nanostructures, the hybrid top-down/bottom-
up growth of AlN nanorods and GaN nanotubes,
and the fabrication of nanopatterned sapphire
substrates for AlN growth. Compared with their
planar counterparts, these 3D nanostructures
enable the reduction or filtering of structural
defects and/or the enhancement of the light
extraction, therefore improving the efficiency of the
final device. These results, achieved on a wafer
scale via DTL and upscalable to larger surfaces, have
the potential to unlock the manufacturing of nano-
engineered III-nitride materials.
Mask-less MOVPE of arrayed n-GaN nanowires on
site- and polarity-controlled AlN/Si templates University of Duisburg-Essen, Dept. Components for High
Frequency Electronics, Faculty of Engineering, and
CENIDE, Duisburg, Germany
CrystEngComm
https://doi.org/10.1039/C9CE01151J
We present a novel approach to attain Ga-polar n-
GaN nanowires on n-Si(111)/AlN templates, by site-
and polarity-controlled metal organic vapor phase
epitaxy. A three-stage process is developed to (i)
form equally-sized Ga-polar GaN islands, (ii) change
the growth direction towards the vertical direction
and finally, to (iii) obtain continuous nanowire
epitaxy. Homogeneous islands are achieved by
minimizing parasitic nucleation and adjusting the
adatom diffusion length to the used nanoimprint
pattern. The influence of the carrier gas
composition on the polarity is studied, achieving
pure Ga-polarity by mostly using nitrogen carrier
gas. Enhancing the Si/Ga-ratio leads to an
amplification of the vertical growth, but also to a
reduced number of NWs. 100% growth is attained
by a height dependent V/III-ratio adjustment. The
results are supported by a qualitative model,
explaining how suppression of multi-pod, parasitic
and inhomogeneous crystallization can be realized
GaNEX | III-N Technology Newsletter No. 83 | 43
by trading off in situ SiNx passivation and localized
GaN growth.
Strongly Confined Excitons in GaN/AlN
Nanostructures with Atomically Thin GaN Layers
for Efficient Light Emission in Deep-Ultraviolet Ioffe Institute, St. Petersburg 194021, Russia
University of Notre Dame, Notre Dame, Indiana 46556,
USA
Université Montpellier, L2C, UMR 5221, 34095
Montpellier Cedex 5, France
NanoLetters
https://doi.org/10.1021/acs.nanolett.9b03517
Fascinating optical properties governed by
extremely confined excitons have been so far
observed in 2D crystals like monolayers of transition
metal dichalcogenides. These materials, however,
are limited for production by epitaxial methods.
Besides, they are not suitable for the development
of optoelectronics for challenging deep ultraviolet
spectral range. Here we present a single monolayer
of GaN in AlN as a heterostructure fabricated by
molecular beam epitaxy, which provides extreme
2D confinement of excitons, being ideally suited for
light generation in the deep ultraviolet. Optical
studies in the samples, supplemented by a group-
theory analysis and first-principle calculations,
evidence a giant enhancement of the splitting
between the dark and bright excitons due to short-
range electron-hole exchange interaction that is a
fingerprint of the strongly confined excitons. The
practical significance of our results is in the
observation of the internal quantum yield of the
room-temperature excitonic emission as high as
~75% at 235 nm.
NON POLAR / SEMI POLAR Information selected by
Philippe de Mierry Impact of 3D growth and SiN x interlayer on the
quality of (11–22) semi-polar GaN grown on m-
plane sapphire School of Electronic Science & Applied Physics, Hefei
University of Technology, 193 Tunxi Road, Hefei 230009,
People's Republic of China
School of Metallurgy and Materials, University of
Birmingham, Birmingham B15 2TT, United Kingdom
Anhui San'an Optoelectronics Co., Ltd., 8 Dongliang
Road, Wuhu 241000, People's Republic of China
Applied Physics Express
https://doi.org/10.7567/1882-0786/ab47b7
We report the growth of semi-polar (11−22) GaN
films with low defect densities on m-plane sapphire
substrates by incorporating a porous SiN x
interlayer in a three-stage growth process. The
linewidth of X-ray diffraction rocking curves for our
semi-polar GaN films decrease with increasing SiN x
deposition time. Cross-sectional transmission
electron microscopy analyzes confirm that the
proposed three-stage growth process greatly
reduces the semi-polar GaN threading dislocation
densities down to 7 × 108 cm−2.
Photoluminescence measurements demonstrate
that InGaN/GaN quantum wells grown on our semi-
polar GaN films provide peak intensities that are 26-
fold greater than those grown on semi-polar GaN by
a standard method.
Untwinned semipolar (10-13) Al x Ga1-x N layers
grown on m-plane sapphire Institute of Materials and Systems for Sustainability,
Nagoya University, Nagoya 464-8601, Japan
School of Engineering, Nagoya University, Nagoya 464-
8603, Japan
Akasaki Research Center, Nagoya University, Nagoya
464-8603, Japan
Semiconductor Science and Technology
https://doi.org/10.1088/1361-6641/ab4d2c
Heteroepitaxial growth of untwinned mono-
crystalline semipolar (10-13) Al x Ga1-x N layers on
(10-13) AlN template was investigated by
metalorganic vapour phase epitaxy. The templates
were initially deposited on (10-10) m-plane
sapphire substrates by directional sputtering.
Different Al/Ga ratios in gas phase were used to
adjust the AlN mole fraction over the entire range
of composition. All the layers show a triclinic
distortion in the wurtzite unit cell due to anisotropic
in-plane strain. The AlN mole fraction of the (10-13)
layers and c-plane co-loaded layers estimated by x-
ray diffraction is comparable. This is consistent both
GaNEX | III-N Technology Newsletter No. 83 | 44
with their comparable effective bandgap energy
estimated from optical transmission measurements
and their near band-edge emission energy obtained
from room-temperature photoluminescence. The
dependence of the bandgap and near band-edge
emission energies on the AlN mole fraction
indicates a bowing parameter of 0.9 eV.
Reduced nonradiative recombination in semipolar
green-emitting III-N quantum wells with strain-
reducing AlInN buffer layers Institute of Applied Physics, Technische Universität
Braunschweig, Mendelssohnstr. 2, 38106 Braunschweig,
Germany
Laboratory for Emerging Nanometrology, Technische
Universität Braunschweig, Langer Kamp 6a, 38106
Braunschweig, Germany
Centre de Recherche sur l'Hétéro-Epitaxie (CNRS-CRHEA),
Rue Bernard Grégory, 06560 Valbonne, France
Applied Physics Letters
https://doi.org/10.1063/1.5118853
Using strain-reducing partially relaxed AlInN buffer
layers, we observe reduced nonradiative
recombination in semipolar green-emitting
GaInN/GaN quantum wells. Since strain is a key
issue for the formation of defects that act as
nonradiative recombination centers, we aim to
reduce the lattice mismatch between GaInN and
GaN by introducing an AlInN buffer layer that can
be grown lattice-matched along one of the in-plane
directions of GaN, even in the semipolar (112⎯⎯2)
orientation. With the increasing thickness, the
buffer layer shows partial relaxation in one
direction and thereby provides a growth template
with reduced lattice mismatch for the subsequent
GaInN quantum wells. Time-resolved
photoluminescence measurements show reduced
nonradiative recombination for the structures with
a strain-reducing buffer layer.
Inhomogeneous Current Injection and Filamentary
Lasing of Semipolar (2021¯) Blue GaN‐Based
Vertical‐Cavity Surface‐Emitting Lasers with Buried
Tunnel Junctions Materials Department, University of California, Santa
Barbara, CA 93106, U.S.A
Department of Electrical and Computer Engineering,
University of California, Santa Barbara, CA 93106, U.S.A
physica status solidi a
https://doi.org/10.1002/pssa.201900718
Blue (202-1) semipolar vertical‐cavity
surface‐emitting lasers with a buried tunnel
junction current aperture are demonstrated under
continuous‐wave operation with a differential
efficiency of 4% and a threshold current of 2.7 mA
for a lasing mode at 452 nm. The effects of the
aperture diameter on these 9λ cavity length devices
are presented, showing that the differential
efficiency increases with aperture size, whereas the
threshold current density remains constant for
apertures larger than 10 μm. Filamentary lasing is
observed in the larger aperture sizes, and it is
suggested that this mode behavior is due to current
injection inhomogeneity across the aperture. This
theory is supported by the correlation between
optical nearfield images and thermal microscopy
images.
MATERIAL / CHARACTERIZATION / EQUIPMENT / NUMERICAL SIMULATION
Information selected by Agnès Trassoudaine (Université d'Auvergne), Yvon
Cordier and Mathieu Leroux (CRHEA-CNRS)
Electric-field-induced simultaneous diffusion of Mg
and H in Mg-doped GaN prepared using ultra-high-
pressure annealing Toyota Central R&D Labs., Inc., Yokomichi, Nagakute
480-1192, Japan
Nagoya University, Nagoya 464-8601, Japan
ULVAC, Inc., 2500 Hagisono, Chigasaki 253-8543, Japan
Institute of High Pressure Physics Polish Academy of
Sciences, 01-142 Warsaw, Poland
Applied Physics Express
https://doi.org/10.7567/1882-0786/ab4934
To investigate Mg diffusion during ultra-high-
pressure annealing, which activates Mg acceptors in
GaN, GaN samples with p–n junctions prepared via
epitaxial growth were annealed at 1573 K under 1
GPa. The profiles of Mg diffusion toward the
underlying n-type layer cannot be explained by a
GaNEX | III-N Technology Newsletter No. 83 | 45
simple diffusion model. We found that H atoms
diffused along with Mg atoms. By considering the
suppressed diffusion of positively charged
interstitial H atoms due to the electric field in the
depletion layer, we could better reproduce the Mg–
H diffusion profiles, suggesting that H atoms play a
key role in the Mg diffusion process.
Metalorganic chemical vapor deposition of
aluminum nitride on vertical surfaces Aalto University, Department of Electrical Engineering
and Automation, PO Box 13500, 00076 Aalto, Finland
Aalto University, Department of Electronics and
Nanoengineering, PO Box 13500, 00076 Aalto, Finland
Murata Electronics Oy, Myllynkivenkuja 6, 01621 Vantaa,
Finland
Journal of Crystal Growth
https://doi.org/10.1016/j.jcrysgro.2019.125345
Metalorganic chemical vapor deposited (MOCVD)
aluminum nitride (AlN) on vertical sidewalls can be
used to implement piezoelectric in-plane actuation
and sensing in microelectromechanical system
(MEMS) sensors. The AlN films should optimally
cover conformally the sidewalls and have good
crystal quality with c-axis oriented microstructure
for optimal piezoelectric properties. Previous
MOCVD AlN research has focused on using AlN as a
buffer layer for other III-nitrides and so far, AlN
growth has not been studied on large vertical
surfaces. In this study, AlN thin films were grown
using MOCVD on vertical sidewalls of fabricated
templates and the conformality and crystal quality
was characterized. The growth template fabrication
was optimized with respect to surface roughness,
the conformal coverage was analyzed by measuring
the thickness profiles of the films, and the crystal
quality was investigated using in-plane XRD and
TEM. The AlN films have good crystal quality
(FWHM 1.70°–3.44°) and c-axis orientation on
vertical Si(1 1 1) sidewalls. However, the
thicknesses of the films reduce approximately at a
rate of 0.8–1.2 nm/m down the sidewall. Lowering
the reactor pressure improved the conformal
coverage while changing the growth mode from
columnar to step-flow, which also improved the
film morphology.
Analysis of growth rate and crystal quality of AlN
epilayers by flow-modulated metal organic
chemical vapor deposition Key Laboratory of Semiconductor Materials Science,
Beijing Key Laboratory of Low Dimensional
Semiconductor Materials and Device, Institute of
Semiconductors, Chinese Academy of Sciences, Beijing,
100083, China
College of Materials Science and Opto-Electronic
Technology, University of Chinese Academy of Sciences,
Beijing, 101408, China
Superlattices and Microstructures
https://doi.org/10.1016/j.spmi.2019.106336
AlN templates have been grown on sapphire by
flow-modulated metal organic chemical vapor
deposition (MOCVD). By analyzing the TMAl duty
ratio R, TMAl utilization ratio β and parasitic
reaction ratio α, we obtained the quantitative
relationship between flow-modulated modes and
growth rate, and then proposed two kinds of flow-
modulated modes to increase the growth rate of
AlN. Besides, we found the continuous growth in
flow-modulated mode can transform the AlN
growth mode from the step-bunching growth into
the two-dimension growth and accordingly improve
the crystal quality of AlN. Finally, the AlN template
with a relatively fast growth rate (0.98 μm/h) and
flat surface morphology (RMS = 0.5 nm) was
obtained by NH3 pulse-flow mode with a small duty
ratio of NH3.
Accurate surface band bending determination on
Ga-polar n-type GaN films by fitting x-ray valence
band photoemission spectrum Vacuum Interconnected Nanotech Workstation (Nano-X),
Suzhou Institute of Nano-Tech and Nano-Bionics
(SINANO), Chinese Academy of Sciences (CAS), Suzhou
215123, China
Suzhou Institute of Nano-Tech and Nano-Bionics
(SINANO), Chinese Academy of Sciences (CAS), Suzhou
215123, China
AIP Advances
https://doi.org/10.1063/1.5120324
The surface band bending in Ga-polar n-type GaN
surfaces, as well as the effect of Si doping levels and
in situ Ar+ ion processing on band bending, was
GaNEX | III-N Technology Newsletter No. 83 | 46
systematically investigated. To precisely determine
the valence band maximum (VBM) of GaN beyond
instrumental and material surface environments by
XPS, a valence band feature fitting procedure based
on photoemission spectra and theoretical densities
of states has been developed. Poisson calculation
with quadratic depletion approximation on surface
potential has been used to model the band bending
and further correct the VBM energy. Then, the
actual surface band bending was correctly
evaluated. Upward band bending of 1.55 ± 0.03 eV
with highly Si doped n-GaN, which is about 0.88 eV
higher than that of the moderately doped sample,
was found. After in situ Ar+ plasma treatment, the
varying degree of band bending was observed
distinctly depending on the Si doping density. The
surface components associated with the Ga/N ratio
and Ga–O bonding concentration on the n-GaN
surface have been used to evaluate the
contribution to surface band bending.
Selective terahertz emission due to electrically
excited 2D plasmons in AlGaN/GaN
heterostructure Department of Physics of Semiconductors and
Nanoelectronics, Peter the Great St. Petersburg
Polytechnic University, 29 Polytechnicheskaya Str., St.
Petersburg 195251, Russia
Institute for Physics of Microstructures of RAS, Nizhny
Novgorod 603950, Russia
Department of Theoretical Physics, Institute of
Semiconductor Physics NASU, Kyiv 03028, Ukraine
Ioffe Institute, 26 Polytechnicheskaya Str., St. Petersburg
194021, Russia
Submicron Heterostructures for Microelectronics
Research and Engineering Center of RAS, 26
Polytechnicheskaya Str., St. Petersburg 194021, Russia
Department of Electronics and Nanoengineering, Aalto
University, P.O. Box 13500, Aalto FI-00076, Finland
Journal of Applied Physics
https://doi.org/10.1063/1.5118771
Terahertz radiation emission from an electrically
excited AlGaN/GaN heterostructure with a surface
metal grating was studied under conditions of two-
dimensional (2D) electron heating by the lateral
electric field. Intensive peaks related to
nonequilibrium 2D plasmons were revealed in the
terahertz emission spectra with up to 4 times
selective amplification of the radiation emission in
the vicinity of 2D plasmon resonance. This selective
emission was shown to be frequency-controllable
by the grating period. Exact spectral positions of the
2D plasmon resonances were preliminarily
experimentally detected with the help of
equilibrium transmission spectra measured at
various temperatures. The resonance positions are
in a satisfactory agreement with the results of
theoretical simulation of the transmission spectra
performed using a rigorous solution of Maxwell’s
equations. The effective temperature of hot 2D
electrons was determined by means of I–V
characteristics and their analysis using the power
balance equation. It was shown that for a given
electric field, the effective temperature of
nonequilibrium 2D plasmons is close to the hot 2D
electron temperature. The work may have
applications in GaN-based electrically pumped
emitters of terahertz radiation.
Impact of dislocations on the thermal conductivity
of gallium nitride studied by time-domain
thermoreflectance Department of Electrical and Computer Engineering,
University of Illinois at Urbana-Champaign, Urbana,
Illinois 61801, USA
Nick Holonyak, Jr. Micro and Nanotechnology
Laboratory, University of Illinois at Urbana-Champaign,
Urbana, Illinois 61801, USA
Journal of Applied Physics
https://doi.org/10.1063/1.5126970
GaN thermal conductivity (κGaN) of hydride vapor
phase epitaxy grown GaN (HVPE GaN), high nitride
pressure grown GaN (HNP GaN), and metal-organic
chemical vapor deposition grown GaN on sapphire
(GaN/sapphire) and on Si(111) (GaN/Si) are
measured as 204.7 (±4.6), 206.6 (±6.8), 191.5
(±10.5), and 164.4 (±3.2) W/m K, respectively, using
the time-domain thermoreflectance technique.
Dislocation densities (σD) of HVPE GaN, HNP GaN,
GaN/sapphire, and GaN/Si are measured as 4.80
(±0.42) × 105, 3.81 (±0.08) × 106, 2.43 (±0.20) × 108,
and 1.10 (±0.10) × 109 cm−2, respectively, using
cathodoluminescence and X-ray diffraction studies.
Impurity concentrations of Si, H, C, and O are
measured by secondary ion mass spectroscopy
GaNEX | III-N Technology Newsletter No. 83 | 47
studies. The relationship between κGaN and σD is
modeled through a new empirical model
κGaN = 210 tanh0.12(1.5 × 108/σD). A modified
Klemens's model, where dislocation induced
scattering strength is increased, is proposed to
explain the experimental rate of decrease in κGaN
with increasing σD. Overall, this work reports how
κGaN of heteroepitaxially-grown GaN can be
estimated based on σD, providing key design
guidelines for thermal management in GaN
semiconductor devices.
Thermal conductivity of crystalline AlN and the
influence of atomic-scale defects Electrical Engineering, Stanford University, Stanford,
California 94305, USA
Thermal and Fluid Engineering, University of Twente,
Enschede 7500 AE, Netherlands
Electrical and Computer Engineering, Cornell University,
Ithaca, New York 14853, USA
Mechanical Engineering, Stanford University, Stanford,
California 94305, USA
Stanford Institute for Materials and Energy Sciences,
SLAC National Accelerator Laboratory, Menlo Park,
California 94025, USA
Physics and Astronomy, University of California, Los
Angeles, California 90095, USA
LITEN, CEA-Grenoble, 17 Avenue des Martyrs, 38054
Grenoble, France
Centre for Modeling and Simulation (CMS), Savitribai
Phule Pune University, Ganeshkhind, Pune 411007,
Maharashtra, India
Materials Science and Engineering, Stanford University,
Stanford, California 94305, USA
Materials Science and Engineering, Cornell University,
Ithaca, New York 14853, USA
Journal of Applied Physics
https://doi.org/10.1063/1.5097172
Aluminum nitride (AlN) plays a key role in modern
power electronics and deep-ultraviolet photonics,
where an understanding of its thermal properties is
essential. Here, we measure the thermal
conductivity of crystalline AlN by the 3ω method,
finding that it ranges from 674 ± 56 Wm−1 K−1 at
100 K to 186 ± 7 Wm−1 K−1 at 400 K, with a value of
237 ± 6 Wm−1 K−1 at room temperature. We
compare these data with analytical models and
first-principles calculations, taking into account
atomic-scale defects (O, Si, C impurities, and Al
vacancies). We find that Al vacancies play the
greatest role in reducing thermal conductivity
because of the largest mass-difference scattering.
Modeling also reveals that 10% of heat conduction
is contributed by phonons with long mean free
paths (MFPs), over ∼7 μm at room temperature,
and 50% by phonons with MFPs over ∼0.3 μm.
Consequently, the effective thermal conductivity of
AlN is strongly reduced in submicrometer thin films
or devices due to phonon-boundary scattering.
An in situ monitored and controlled etch process
to suppress Mg memory effects in MOCVD GaN
growth on Si substrate Centre for Nano Science and Engineering, Indian Institute
of Science, Bangalore 560012, India
Department of Electrical Communication Engineering,
Indian Institute of Science, Bangalore 560012, India
Materials Research Centre, Indian Institute of Science,
Bangalore 560012, India
Semiconductor Science and Technology
https://doi.org/10.1088/1361-6641/ab5006
Mg is the most common p-type dopant in III-nitride
devices and is becoming increasingly important in
the design and development of transistors for
power applications. The diffusion of Mg atoms to
adjacent layers during growth has been a persistent
problem. We report on a simple method involving
in situ etching by hydrogen, the most commonly
used carrier gas in nitride growth, for suppressing
Mg diffusion. This method can be implemented
during growth itself without removing the wafer
from the chamber and can be controlled by in situ
monitoring. A Mg concentration decay rate of 24
nm/dec, is reported for the etched sample
compared to 160 nm/dec for the unetched one. An
increase in 2DEG mobility in AlGaN/GaN HEMT
structures on silicon substrate from 591 cm2 V−1
s−1 for the unetched sample to 1214 cm2 V−1 s−1
for the etched sample was observed. Capacitance–
voltage studies to understand the effect of diffused
Mg atoms on conduction channel are also reported.
GaNEX | III-N Technology Newsletter No. 83 | 48
High-mobility two-dimensional electron gases at
AlGaN/GaN heterostructures grown on GaN bulk
wafers and GaN template substrates School of Electrical and Computer Engineering, Cornell
University, Ithaca, NY 14853, United States of America
Department of Materials Science and Engineering,
Cornell University, Ithaca, NY 14853, United States of
America
Kavli Institute for Nanoscale Science, Cornell University,
Ithaca, NY 14853, United States of America
Applied Physics Express
https://doi.org/10.7567/1882-0786/ab512c
We report a comparative study of the mobility of
two-dimensional electron gases (2DEG) formed at
AlGaN/GaN heterostructures by simultaneously
growing on substrates with very different
dislocation densities. The mobility is seen to depend
on the 2DEG charge density directly, but
surprisingly, dislocations do not cause a discernible
impact on the mobility of the samples within the
measured region <25 000 cm2 V−1 s−1. This
experimental observation questions the generally
accepted belief that dislocations are one of the
dominant low-temperature scattering mechanisms
for low-density 2DEG at AlGaN/GaN structures.
Experimental Determination of Velocity-Field
Characteristic of Holes in GaN Department of Electrical Engineering, Stanford
University, CA, 94305 USA
Department of Electrical and Computer Engineering,
University of California, Davis, CA, 95616 USA
IEEE Electron Device Letters
https://doi.org/10.1109/LED.2019.2953873
This study presents a photo-assisted method to
measure the drift velocity of carriers in
semiconductors, and successfully used to determine
the drift velocity of holes in GaN. A p-i-n diode with
a buried p-type layer was designed and fabricated
on a free-standing GaN substrate. By reverse-
biasing the p-i-n diode and illuminating the cathode
layer using an ultraviolet light simultaneously,
photo-generated holes were injected into the
depletion region and accelerated by the electric
field to reach the saturation velocity. The drift
velocity (vd). electric field (E) characteristic can be
obtained from the photocurrent induced by photo-
generated holes. The measured hole drift velocity
can be written as vd= µLF E/[1+(µLF E/vsat)β]1/β,
where µLF=17 cm2/Vs is the low-field hole mobility,
vsat=6.63×106 cm/s is the saturation velocity,
β=1.75 is the fitting parameter. The method
presented in this study is a unique way of
determining the saturation drift velocity of holes in
GaN.
Modeling the simultaneous effects of thermal and
polarization in InGaN/GaN based high electron
mobility transistors Department of Physics, College of Science, Majmaah
University, Al Zulfi, 11932, Saudi Arabia
Electronics and Microelectronics Laboratory, Faculty of
Science of Monastir, University of Monastir, Monastir,
5019, Tunisia
Quantum and Statistical Physics Laboratory, Faculty of
Sciences of Monastir, University of Monastir, Monastir,
5019, Tunisia
Laboratoire de Matière Condensée et Sciences
Interdisciplinaires (LaMCScI), Group of Optoelectronic of
Semiconductors and Nanomaterials, ENSET, Mohammed
V University in Rabat, Morocco
Université de Lorraine, LCP-A2MC, F-57000, Metz, France
Department of Mechanical and Industrial Engineering,
College of Engineering, Majmaah University, Al-Majmaah
11952, Saudi Arabia
Computer Science Department, College of Science and
Humanities at Alghat, Majmaah University, Majmaah
11952, Saudi Arabia
Computer and Embedded System Laboratory, Sfax
University, Sfax, 3011, Tunisia
Optik
https://doi.org/10.1016/j.ijleo.2019.163883
In this paper, we propose the modeling of the two-
dimensional electron gas (2DEG) density in
InGaN/GaN hetero-interface based high electron
mobility transistors (HEMT). The Schrodinger-
Poisson equations, as well as the polarization-
induced charges, have been utilized. The
temperature effect on the effective mass, band gap
energy, dielectric constant and the lattice thermal
expansion is taken into account. Our numerical
calculation shows that the 2DEG density decreases
with temperature. This is due to the shrinkage of
the conduction band offset at high temperatures.
GaNEX | III-N Technology Newsletter No. 83 | 49
The improvement of the sheet carrier density and
the carrier confinement at the InGaN/GaN hetero-
interface based heterostructures is made at low
temperature.
Influence of plasma-activated nitrogen species on
PA-MOCVD of InN Department of Physics and Astronomy, Georgia State
University, Atlanta, Georgia 30303, USA and Center for
Nano-Optics, Georgia State University, Atlanta, Georgia
30303, USA
Department of Geosciences, Georgia State University,
Atlanta, Georgia 30303, USA
Applied Physics Letters
https://doi.org/10.1063/1.5126625
We report on the influence of various plasma
species on the growth and structural properties of
indium nitride in plasma-assisted metalorganic
chemical vapor deposition. Atomic emission
spectroscopy was used to quantify the molecular,
neutral, and ionized nitrogen species
concentrations above the growth surface.
Reflectance and Raman spectroscopy and X-ray
diffraction techniques were used to characterize
the grown InN films. It has been found that ionized
rather than molecular or neutral nitrogen species is
positively correlated with the InN growth rate. We
conclude that InN formation in the present case is
due to the chemical combination of atomic nitrogen
ions with indium.
Improving Ni/GaN Schottky diode performance
through interfacial passivation layer formed via
ultraviolet/ozone treatment Department of Electronics and Electrical Convergence
Engineering, Hongik University, Sejong, 30016, Republic
of Korea
School of Electronics Engineering, Kyungpook National
University, Daegu, 41566, Republic of Korea
Current Applied Physics
https://doi.org/10.1016/j.cap.2019.11.017
Electrical passivation has a significant effect on
metal-semiconductor (MS) device operations
including performance and reliability. In this study,
the improvement in performance of Ni/GaN
Schottky diodes (SDs) through an ultraviolet/ozone
(UV/O3) interface treatment is investigated and the
mechanism of carrier conduction at the MS junction
interfaces is analyzed. The formation of surface
oxide layer at the MS interface through the UV/O3
treatment is confirmed by the measurements using
X-ray photoelectron spectroscopy, contact angle,
and atomic force microscopy. The atomic intensity
and surface energy increased and surface
roughness improved through the implementation of
oxide layer. Electrical measurements reveal reduced
leakage and improved breakdown voltage and are
used to determine the Schottky barrier height and
Richardson constant of the Ni/GaN MS SDs. The
enhancement in the entire performance of the MS
SDs is attributed to the passivation of defect
centers at the dislocation-related pits through the
formation of oxide layer with the UV/O3 treatment,
which thereby improves the carrier transfer
properties of Ni/GaN SDs.
Field Dependent Ultrafast Carrier Dynamics in
InGaN/GaN p-i(MQW)-n Structure Key Laboratory of Polar Materials and Devices,
Department of Optoelectronics, East China Normal
University, Shanghai 200241, P. R. China
Department of Physics, Beijing University of Science and
Technology, Beijing 100083, P. R. China
Superlattices and Microstructures
https://doi.org/10.1016/j.spmi.2019.106354
Field dependent ultrafast carrier dynamics in
InGaN/GaN multiple quantum wells (MQW)
embedded within a p-i-n structure (InGaN/GaNp-
i(MQW)-n) was systematically investigated by
photoluminescence (PL), time-resolved PL and
transient differential reflectivity measurements. We
observed two PL peaks (centered at 450nm and
500nm) originated from MQW and localized defect
states. Excitation density dependent PL spectra
shows that the amplified spontaneous emission
participates in the quantum well emission.
Surprisingly, time-resolved PL clearly exhibits that
quantum well emission has an extremely long decay
time, which is much slower than the lower energy
peak from defect states. We infer that the built-in
PN field affects dominantly the carrier
recombination more than the piezoelectric
polarization field. The distinct excitation-dependent
GaNEX | III-N Technology Newsletter No. 83 | 50
decay kinetic allows us to identify the dynamic
interplay of screening and descreening effect by
photo-generated carriers. Additionally transient
reflectivity measurements also exhibit that carrier
thermalization process becomes faster with
increasing excitation density, which could be due to
the amplified spontaneous emission.
Confirmation of the compensation of
unintentional donors in AlGaN/GaN HEMT
structures by Mg-doping during initial growth of
GaN buffer layer Raja Ramanna Centre for Advanced Technology, Indore,
452013, Madhya Pradesh, India
Homi Bhabha National Institute, Training School
Complex, Anushakti Nagar, Mumbai, 400094, India
Journal of Luminescence
https://doi.org/10.1016/j.jlumin.2019.116904
Effect of partial Mg doping on the compensation of
unintentional donors at epilayer/template interface
and in the GaN channel layer of AlGaN/GaN High
Electron Mobility Transistor (HEMT) structures is
investigated. Photoluminescence excitation
spectroscopy and surface photovoltage
spectroscopy measurements reveal the signature of
high density of unintentional shallow donors and
deep level defects throughout the GaN buffer layer
along with a strong dominance at the GaN/Fe-GaN
template interface. Mg doping during the initial
growth of GaN buffer layer on Fe-GaN template is
found to compensate unintentional donors which
therefore reduces the density of deep defects. Hall
measurements also confirm systematic
improvement in the electronic transport properties
of AlGaN/GaN HEMT for an optimized Mg doping.
Further, Mg-doping driven enhancement of 2-
dimensional electron gas confinement at
AlGaN/GaN interface is also observed in the
spectroscopy measurements. It is shown that the
electrical and optical properties can be improved by
an optimized Mg-doping of the initial part of GaN
buffer layer in AlGaN/GaN HEMT structures.
In Situ Synchrotron X-ray Diffraction Reciprocal
Space Mapping Measurements in the RF-MBE
Growth of GaInN on GaN and InN Department of Applied Physics, School of Advanced
Engineering, Kogakuin University, Tokyo192-0015, Japan
Synchrotron Radiation Research Center, National
Institutes for Quantum and Radiological Science and
Technology (QST), Hyogo 679-5148, Japan
Department of Electrical & Electronic Engineering,
Ritsumeikan University, Kyoto 525-8577, Japan
Crystals
https://doi.org/10.3390/cryst9120631
In this work, in situ synchrotron X-ray diffraction
reciprocal space mapping (RSM) measurements
were carried out for the radio-frequency plasma-
assisted molecular beam epitaxy (RF-MBE) growth
of GaInN on GaN and InN layers, which were also
grown by RF-MBE on commercialized GaN/c-
sapphire templates. In situ XRD RSM measurements
were performed using an MBE apparatus directly
coupled to an X-ray diffractometer at the beamline
of the synchrotron radiation facility SPring-8. It was
observed in situ that both lattice relaxation and
compositional pulling occurred during the initial
growth stage, reducing the strain of GaInN on GaN
and InN. Different initial growth behaviors of GaInN
on GaN and InN were also observed from the
results of the evolution of GaInN integrated peak
intensities.
Suppression of Green Luminescence of
Mg‐Ion‐Implanted GaN by Subsequent
Implantation of Fluorine Ions at High Temperature ASEE Postdoctoral Fellow residing at U.S. Naval
Research Laboratory, Washington, DC, 20375, USA
U.S. Naval Research Laboratory, Washington, DC, 20375,
USA 3Dept. of Physics, University of Notre Dame, Notre
Dame, IN, 46556, USA
NRC Postdoctoral Associate residing at U.S. Naval
Research Laboratory, Washington, DC, 20375, USA
physica status solidi b
https://doi.org/10.1002/pssb.201900554
Gallium nitride (GaN) samples implanted with
magnesium (Mg) and fluorine (F) ions were
investigated by photoluminescence (PL)
measurement. In low‐temperature PL
GaNEX | III-N Technology Newsletter No. 83 | 51
measurements, the characteristic green
luminescence (GL) band attributable to nitrogen
vacancies (VNs) is observed in Mg‐ion‐implanted
GaN. Since VNs are likely to act as donors,
suppressing their formation is essential to realizing
p‐type conductivity. The energy required for a F
impurity to replace VN in GaN and eventually form
F on a N site decreases when the Fermi level
approaches to the valence band maximum, and
therefore F was employed as a subsequent
implantation element to compensate for VN. The
GL band peak disappeared upon implanting Mg and
F ions at a high temperature and adjusting the F
concentration to an appropriate value. This result
suggests that VNs generated by Mg ion
implantation can be suppressed by using an
element with a lower formation energy than VN.
Deep‐Level Defects and Impurities in InGaN Alloys Materials Department, University of California, Santa
Barbara, California 93106-5050, USA
Center for Computational Materials Science,US Naval
Research Laboratory, Washington, D.C. 20375, USA
Department of Physics and Astronomy, Stony Brook
University, Stony Brook, New York 11794-3800, USA
Center for Computational Quantum Physics, Flatiron
Institute, 162 5th Avenue, New York, NY 10010
Department of Materials Science and Engineering,
University of California, Berkeley, CA 94720-1760, USA
Center for Physical Sciences and Technology (FTMC),
Vilnius LT-10257, Lithuania
physica status solidi b
https://doi.org/10.1002/pssb.201900534
In this study, density functional theory calculations
with a hybrid functional are used to examine the
charge‐state transition levels of native point defects
and impurities in InGaN alloys, with the goal of
identifying centers that play a role in
defect‐assisted recombination. Explicit alloy
calculations are used to monitor the dependence of
defect levels on indium content and distribution of
In atoms. The relative shift (or lack thereof) of the
charge‐state transition levels of the different
defects is explained by the atomic character of the
defect state and whether it is derived from
valence‐band or conduction‐band states of the host
material or acts as an atomic‐like impurity. The
various possible atomic configurations of In and Ga
cations for a given composition of InGaN lead to a
distribution of charge‐state transition levels.
Defects on the nitrogen site lead to a larger spread
in levels compared with defects on the cation site.
Role of Capping Material and GaN Polarity on Mg
Ion Implantation Activation
physica status solidi a
https://doi.org/10.1002/pssa.201900789
Ion implantation of magnesium for p‐type GaN
presents many opportunities, however, activation
has proven difficult due to the decomposition of
GaN at relevant annealing temperatures. Here we
present testing the efficacy of multiple in‐situ and
ex‐situ caps based on aluminum nitride and silicon
nitride for GaN protection during annealing.
Photoluminescence shows better activation for
in‐situ MOCVD grown aluminum nitride caps
compared to ex‐situ sputtered aluminum nitride
and the best performance by ex‐situ PECVD silicon
nitride. Furthermore, only samples annealed at the
highest temperatures tested showed preferential
growth of UV luminescence to yellow‐green
luminescence reinforcing the need for better
capping solutions and higher temperature
annealing.
Effect of Wafer Off‐Angles on Defect Formation in
Drift Layers Grown on Free‐Standing GaN
Substrates Graduate School of Electrical and Electronics
Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui
910–8507, Japan
Sciocs Company Ltd., Hitachi-Shi, Ibaraki 319-1418, Japan
Research Centre for Micro-Nano Technology, Hosei
University, 3-11-15 Midori-cho, Koganei, Tokyo 184–
0003, Japan
physica status solidi b
https://doi.org/10.1002/pssb.201900561
The effect of the surface off‐angle toward either the
a‐ or m‐axis on the defect formation is
characterized using deep‐level transient
spectroscopy (DLTS) in conjunction with the carrier
concentration for Ni Schottky contacts formed on
GaNEX | III-N Technology Newsletter No. 83 | 52
n‐GaN drift layers. In both noncontact and
conventional capacitance–voltage results, off‐angle
dependence on carrier concentration is observed.
For all samples, a large dominant peak appears at
approximately 270 K in the DLTS spectra and is
attributed to E3 (EC − 0.57–0.61 eV) defects. Carbon
atoms can act as carrier compensators and form E3
defects. These results can be interpreted based on
how C incorporation during crystal growth depends
on the off‐angle.
Growth of AlGaN/InGaN/GaN Heterostructure on
AlN Template/Sapphire Wide-gap semiconductor group, National Institute for
Materials Science, Tsukuba, 305-0044, Japan
High Magnetic Field Measurement Group, National
Institute for Materials Science, Tsukuba, 305-0003, Japan
Department of Condensed Matter Physics, Graduate
School of Science, Hokkaido University, Sapporo 060-
0810, Japan
Department of Electric Engineering and Electronics,
Graduate School of Engineering, Kogakuin University,
Hachioji, Tokyo 192-0015, Japan
physica status solidi b
https://doi.org/10.1002/pssb.201900524
GaN films are grown directly on AlN
templates/sapphire substrates without using
low‐temperature (LT) buffer layers by metalorganic
chemical vapor deposition. AlN templates are
complimentarily deformed at the initial growth of
GaN, adjusting the a‐lattice constant and tilting
crystal orientation slightly. Compared with the film
on sapphire substrates using an LT buffer layer, the
GaN on the AlN template forms a smoother surface
and has better crystalline quality after a shorter
growth time at a lower temperature. Higher‐quality
InGaN films on the GaN/AlN template are
subsequently grown to optimize the thickness
exhibiting the minimum Urbach energy which is
evaluated by photothermal deflection
spectroscopy. A high‐quality AlGaN/InGaN
heterostructure is fabricated in which the
Shubnikov–de Haas oscillation can be clearly
observed from the electron gas of the InGaN
channel at the interface.
The Influence of Ga–OH Bond at Initial GaN
Surface on the Electrical Characteristics of
SiO2/GaN Interface Nara Institute of Science and Technology, Ikoma Nara,
Japan
physica status solidi b
https://doi.org/10.1002/pssb.201900368
Herein, the influence of the Ga–OH bond at the GaN
surface on the electrical characteristics of the
SiO2/GaN metal‐oxide semiconductor structure is
investigated. The GaN surface is modified by three
different surface treatments (O2 annealing, wet
annealing, and ultraviolet [UV]/O3 treatment). The
Ga–OH bond is evaluated by X‐ray photoelectron
spectroscopy and characterized by capacitance–
voltage (CV) measurements and a positive bias
stress test. Increasing the ratio of Ga–OH bonds at
the SiO2/GaN interface decreases the net fixed
charge at the SiO2/GaN interface in the CV
measurements and increases the voltage shift in the
stress test. Therefore, the Ga–OH bond at the
SiO2/GaN interface develops a negative charge and
behaves as an electron trap. The undesirable
influence of the Ga–OH‐related traps is reduced by
low‐temperature annealing.
Prediction of dislocation density in AlN or GaN
films deposited on (0001) sapphire Univ. Grenoble Alpes, CNRS, Grenoble INP, SIMAP,
Grenoble, France
Sil’Tronix Silicon Technologies, Archamps, France
Journal of Materials Science
https://doi.org/10.1007/s10853-019-04240-x
The origin of threading dislocations (TDs) in nitride
films is not completely understood but it is well
established that they degrade the film properties.
This work investigates the assumption that they
arise from the interface between the film and
sapphire substrate owing to small in-plane rotations
between nitride domains. Bollmann’s formalism is
first used to determine the characteristics of
dislocations at the nitride film/sapphire interface
that compensate both for the parametric misfit and
a small in-plane rotation of the film as frequently
observed. It is shown that the dislocation density
GaNEX | III-N Technology Newsletter No. 83 | 53
and line direction depend on the rotation angle.
When islands grow and coalesce in the nucleation
layer, some interfacial dislocations orientate along
[0001] in the boundaries between domains and
transform to so-called TDs. The amount of TDs lying
in the boundaries between nitride domains is
calculated as a function of the rotation angle.
Estimations of TD density in the nucleation layer are
deduced for a range of domain sizes and compared
with experimental values of the literature.
Study of electronic properties on the n-GaN (0001)
surface with points defects Department of Optoelectronic Technology, School of
Electronic and Optical Engineering, Nanjing University of
Science and Technology, Nanjing, People’s Republic of
China
Applied Physics A
https://doi.org/10.1007/s00339-019-3142-3
The influence of defects on the surface of the semiconductor is irreversible. The influence of
intrinsic point defects on the electronic properties of n-doped GaN (0001) surface is studied based on the first principles. The results show that, the N interstitial defect (Ni) and Ga Vacancy (VGa) are the more easily formed in the case of Si doping. The defect level generated by an appropriate amount of defects contributes to the transition of electrons, thereby improving the n-type conductivity characteristics. In particular, the Ga vacancy makes the work function drop significantly, which promotes the emission of electrons. However, once the defects inside the material exceed a certain level, any defects will play a counterproductive role. This paper could provide some guidance for the preparation of n-GaN optoelectronic devices.
GaNEX | III-N Technology Newsletter No. 83 | 54
PRESS RELEASE Technical and economic information selected by Knowmade
ELECTRONICS
RF GaN market growth to accelerate to over $1.7bn in 2023: SEDI, Wolfspeed and Qorvo to benefit SemiconductorToday
Revenue from RF gallium nitride (GaN)-enabled devices grew nearly 22% in 2018 and will accelerate, surpassing
$1.7bn in 2023, forecasts the Strategy Analytics Advanced Semiconductor Applications (ASA) report ‘RF GaN
Market Forecast: 2018 - 2023 (Data Tables)’. The drivers for this growth will be the continuing deployments of
4G and emerging 5G base-stations, along with a variety of defense applications.
“Base stations represent the largest source of GaN revenue,” notes Eric Higham, director of the Advanced
Semiconductor Applications (ASA) service and the Advanced Defense Systems (ADS) service. “Trade tensions
between the US and China remains a wildcard, but Sumitomo Electric Device Innovations and Wolfspeed will
remain the dominant GaN suppliers for base-station applications,” he adds. “The defense market, primarily
radar and communications applications, is seeing strong growth from new systems and major platform
upgrades. This is also providing fuel for the GaN growth engine and should bode well for companies like Qorvo
and Wolfspeed.”
Transphorm ships over half a million GaN power devices for multi-kW-class applications SemiconductorToday
Transphorm Inc of Goleta, near Santa Barbara, CA, USA — which designs and manufactures JEDEC- and AEC-
Q101-qualified 650V gallium nitride (GaN) field-effect transistors (FETs) — says it has shipped more than
500,000 high-voltage GaN FETs.
Customers in the broad industrial, infrastructure & IT and PC gaming markets have publicly announced in-
production devices built with Transphorm’s GaN technology, illustrating the rising confidence in GaN solutions,
says the firm.
In fact, industry analyst firm IHS Markit Technology (now a part of Informa Tech) forecasts that total GaN power
discrete, module and system IC revenue will reach $1.2bn by 2028 (‘SiC & GaN Power Semiconductors Report’,
May 2019). About $750m of that (almost two-thirds of the total market) will be driven by high-voltage GaN
solutions.
“We came to market with the most robust, two-chip normally-off device at a time when the industry was more
familiar with single-chip normally-off silicon MOSFETs,” says Transphorm’s co-founder & chief operating officer
Primit Parikh. “As proven by our public momentum and also that of other reputable manufacturers like Power
Integrations in the consumer adapter space, the two-chip normally-off GaN solution is the most practical high-
voltage GaN FET design today,” he adds. “In fact, it’s this design that enables Transphorm’s GaN to deliver high
performance with strong robustness, which has led to more than 5 billion hours (with <2 FIT) of field reliability
data to date.”
GaNEX | III-N Technology Newsletter No. 83 | 55
Transphorm says that its adoption continues to be driven largely by the quality and reliability (Q+R) of its
products, which is backed by its robust normally-off GaN platform, strong control of its epitaxial process, and
manufacturing capability — positioned to meet the volume and quality requirements of various cross-industry
markets from consumer adapters to automotive.
“Following our success in the core higher-power markets targeted by GaN, we’re also working with customers in
fast-growing markets that are underserved by silicon such as consumer adapters and set-top boxes,” says Philip
Zuk, VP of worldwide technical marketing & North American sales. “Consider that the majority of products
we’ve shipped to date were targeted for higher-power applications. Those 500,000-plus 650V FETs equate to
more than 4 million lower-power (sub-100W) FETs, demonstrating our volume production capabilities.”
A year ago, Transphorm released the first complete set of validation data for high-voltage GaN power
semiconductors. The firm has now formally released its latest field reliability data. With more than 5 billion
hours in the field, Transphorm’s GaN technology currently has a <2.0 FIT rate at <19.8 PPM per year.
Nexperia enters GaN FET market SemiconductorToday
Nexperia BV of Nijmegen, Netherlands, which manufactures discrete and MOSFET components and analog &
logic ICs, has announced its entry into the gallium nitride (GaN) field-effect transistor (FET) market with the
introduction of the 650V GAN063-650WSA, which has a gate-source voltage (VGS) of +/-20V, a temperature
range of -55°C to +175°C, a low on-resistance (RDS(on)) of down to 60mΩ, and fast switching to offer very high
efficiency.
In April 2018, Cree Inc of Durham, NC, USA signed a non-exclusive, worldwide, royalty-bearing patent license
agreement that provided Nexperia with access to its GaN power device patent portfolio, addressing device
structures, materials and processing improvements, and packaging technology.
Nexperia is targeting high-performance application segments including hybrid and all-electric vehicles (xEV),
data centers, telecom infrastructure, industrial automation and high-end power supplies. The firm says that its
GaN-on-silicon process is robust and mature with proven quality and reliability, and that it is highly scalable as
wafers can be processed in existing silicon fabrication facilities. Also, the device is available in the industry-
standard TO-247, allowing the benefit of GaN’s performance in a familiar package.
“This is a strategic move for Nexperia into the high-voltage area, and we can now deliver technology suitable for
xEV power semiconductor applications,” says Toni Versluijs, general manager of Nexperia MOS Business Group.
“Our GaN is a technology that is ready for volume production, and with scalability to meet high-volume
applications,” he adds. “The automotive sector is a key focus for Nexperia and one which is forecast to grow
significantly for two decades as electric vehicles replace those powered by traditional internal combustion
engines as the preferred means of personal and public transport.”
The GAN063-650WSA GaN FET is the first in a portfolio of GaN devices that Nexperia is developing to address
the automotive, communication infrastructure and industrial markets.
GaNEX | III-N Technology Newsletter No. 83 | 56
SweGaN, IEMN and Linköping University unveil Transmorphic Heteroepitaxy GaN-on-SiC growth process for power devices SemiconductorToday
A project funded by the European Union’s Horizon 2020 research and innovation program has contributed to
custom gallium nitride on silicon carbide (GaN-on-SiC) epitaxial wafer manufacturer SweGaN AB of Linköping,
Sweden collaborating with Linköping University and IEMN (a French research group dedicated to high-power
devices) to develop the new epitaxial growth mechanism Transmorphic Heteroepitaxy for producing next-
generation GaN-on-SiC power devices (‘Transmorphic Epitaxial Growth of AlN Nucleation Layers on SiC
Substrates for High-Breakdown Thin GaN Transistors’, Applied Physics Letters, vol115, no22, 25 November
2019).
Specifically, SweGaN collaborated with the scientists in electron microscopy and modeling at Linköping
University and senior researchers at IEMN to explore the nature of the new epitaxial growth mechanism and the
potential of SweGaN’s QuanFINE hybrid GaN–SiC heterostructures for high-power device applications (joining to
the firm’s existing product portfolio for RF components and devices).
“Not only is this a high-impact innovation, but it comes together with a scientific discovery of a novel epitaxial
growth mechanism, which we coin transmorphic,” says the paper’s co-author Lars Hultman, professor at
Linköping University and member of the Royal Swedish Academy of Sciences.
“This breakthrough could significantly reduce the power loss for high-power devices, which would truly manifest
the superiority of GaN power devices over silicon super-junction power devices and silicon carbide MOSFETs for
650V-rated devices,” says chief technology officer Jr-Tai Chen.
The new results show Transmorphic Heteroepitaxy growth where less than 1nm-thick atomic interlayers with
ordered vacancies are created to sufficiently accommodate the lattice mismatch at the interface between the
first epilayer and the substrate.
SweGaN highlights the following features:
• The new growth mechanism suppresses the formation of structural defects in the beginning of the
epitaxy, which enables grain-boundary-free aluminium nitride (AlN) nucleation layers and subsequent
high-quality buffer-free GaN-based heterostructures to be realized on SiC substrates.
• A GaN high-electron-mobility transistor (HEMT) heterostructure with a total thickness of less than
300nm grown by the transmorphic epitaxial scheme on a semi-insulating SiC substrate shows a lateral
critical breakdown field of ~2MV/cm and a vertical breakdown voltage of ≥3kV (measured by senior
researchers at IEMN).
• The critical breakdown field is nearly three times higher than that of GaN-on-Si epiwafers grown by the
conventional thick-buffer approach. So, the device’s ON-resistance has the potential to be lower by
more than one order of magnitude than the value achievable currently, according to Baliga’s figure of
merit (BFOM).
“With these new results, SweGaN will now extend the focus of its QuanFINE technology to include the global
power market in addition to RF devices, particularly in Asia showing the most hunger for new-generation GaN
power devices,” says Chen. “We anticipate releasing more new findings on the performance of QuanFINE based
power devices in the near future.”
GaNEX | III-N Technology Newsletter No. 83 | 57
FBH-led project ‘power transistors based on AlN (ForMikro-LeitBAN)’ launched SemiconductorToday
Coordinated by the Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik (FBH) of Berlin,
Germany, the recently launched joint project ‘power transistors based on AlN (ForMikro-LeitBAN)’ aims to
develop highly efficient power semiconductors that can pave the way for a wide range of novel applications –
from e-mobility to artificial intelligence.
Smart energy supply, electro-mobility, broadband communication systems and applications of artificial
intelligence (AI) are driving constant growth in the number of interacting and interconnected systems. However,
with the growing number of systems and increasing data traffic, primary energy consumption is also rising.
Electrical energy must be converted at all times to be usable by the various systems, which is why the need for
electrical conversion is also increasing. In Europe alone, it is estimated that more than 3TeraWatt-hours of
energy (the amount of electricity produced by a medium-sized coal-fired power plant) are lost by energy
conversion each year. Efficient energy conversion is therefore key for applications like AI and Industry 4.0
(representing the fourth industrial revolution based on digitization processes in manufacturing). The
prerequisite for this are efficiently switching power semiconductors that enable high power density. Used to a
large extent, this would result in noticeable energy savings and make a relevant contribution to CO2 reduction.
The project aims to develop aluminium nitride (AlN) semiconductor material for this task, to test it with suitable
devices and to qualify it for future applications in systems. Until 2023, the project will be funded with €3.3m by
Germany’s Federal Ministry of Education and Research (BMBF) within the program ForMikro (Forschung für
neue Mikroelektronik).
Picture: Gallium nitride amplifier from an earlier FBH project. In the ForMikro-LeitBAN project, the technology
for millimeter waves is to be transferred to aluminum nitride. (© FBH/schurian.com)
Aluminum nitride – starting material with potential
The efficiency of systems is limited by static and dynamic power losses of semiconductors, determined by the
respective material. It is becoming increasingly difficult to increase the efficiency of electrical converters and
power amplifiers with conventional silicon-based power components. New semiconductor materials with
improved properties must therefore be investigated and brought to market maturity, says FBH. The project
partners aim to use aluminum nitride (AlN), which has so far been little studied for electronic applications but
GaNEX | III-N Technology Newsletter No. 83 | 58
offers up to 10,000 times less conduction losses than silicon devices. It is also characterized by very high
breakdown strength and thermal conductivity – ideal prerequisites for power semiconductors with high energy
density and efficiency. Free-standing insulating AlN wafers are to be used and qualified as the substrate.
Compared to AlN epitaxy on foreign substrates such as silicon carbide (SiC), the dislocation density can be
reduced by five orders of magnitude. This offers the potential for fast and efficient switching devices while
maintaining high reliability.
Full process chain – from crystal growth to system demonstrators
From a conceptual point of view, the novel AlN components are based on well-researched GaN technology. A
new aspect is the transition from conventional foreign substrates such as silicon carbide, sapphire or silicon to
free-standing AlN substrates. ForMikro-LeitBAN is researching the development of such AlN wafers and testing
them in a tailor-made device process. Test systems for millimeter-wave applications and for power electronic
energy converters qualify the new highly efficient AlN devices for applications in corresponding systems.
ForMikro-LeitBAN involves the following partners, which collectively span the entire value chain (from AlN
wafers to both millimeter-wave and power electronic systems):
• Ferdinand-Braun-Institut (FBH): AlN device design and development;
• Fraunhofer IISB, Erlangen (IISB): AlN crystal growth, wafer manufacturing;
• TU Bergakademie-Freiberg (IAP): Process module development, analytics;
• Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU): material analysis;
• Brandenburgische Technische Universität Cottbus-Senftenberg (BTU): AlN millimetre-wave systems;
• Technische Universität Berlin (TUB): AlN power electronic systems.
The technology will also be prepared for transfer of into an industrial environment. The consortium’s work is
hence being supported by an industrial advisory board comprising Infineon for power electronics, UMS for
millimetre-wave technology and III/V-Reclaim for the recycling of AlN wafers. A respective follow-up project is
also planned.
Sumitomo Electric to begin 150mm GaN-on-SiC production after ordering Aixtron AIX G5+ MOCVD system SemiconductorToday
Deposition equipment maker Aixtron SE of Herzogenrath, near Aachen, Germany says that Japan’s Sumitomo
Electric Device Innovations Inc (SEDI), a subsidiary of Sumitomo Electric Industries Ltd, has ordered an AIX G5+
metal-organic chemical vapor deposition (MOCVD) system with 8x6-inch wafer configuration (for delivery in
2019) in order to expand its production capacity of gallium nitride-on-silicon carbide (GaN-on-SiC) radio
frequency (RF) devices for wireless applications such as radars, satellite communication and base stations for
the rapidly expanding 5G mobile networks.
SEDI has already been relying on Aixtron’s Showerhead technology for the production of 4-inch GaN high-
electron-mobility transistor (HEMT) epitaxial wafers. The progressive deployment of 5G networks but also the
introduction of new technologies like beamforming is expected to drive a rapid upturn in demand, steering the
adoption of more efficient 6-inch substrates for RF applications on Aixtron’s proven Planetary systems.
The new reactor is equipped with an EpiCurve TT metrology system as well as Auto-Feed Forward and P400 UV
Pyrometer Close Loop temperature control. Aixtron adds that the system’s wafer uniformity and precise process
control is especially important for device production on cost-intensive silicon carbide wafers.
GaNEX | III-N Technology Newsletter No. 83 | 59
Sumitomo Electric Device Innovations Inc has an established portfolio of RF components, including a range of
GaN HEMT devices for radar, mobile phone base stations, and general applications. The GaN-on-SiC HEMT
devices enable high power amplification at operating frequencies of 28-40GHz and beyond, as required by new
5G communication standards.
Navitas’ GaNFast Power ICs used by HYPER in smallest 100W 4-port wall charger SemiconductorToday
Navitas Semiconductor Inc of El Segundo, CA, USA has announced its partnership with California-based HYPER
by Sanho Corporation to introduce the HyperJuice 100W 4-port charger with GaNFast power IC technology to
achieve what is reckoned to be the world’s smallest and lightest portable form-factor.
Founded in 2014, Navitas introduced what it claimed to be the first commercial gallium nitride (GaN) power ICs.
The firm says that its proprietary ‘AllGaN’ process design kit (PDK) monolithically integrates GaN power field-
effect transistors (FETs) with GaN power, analog and logic circuits, enabling faster charging, higher power
density and greater energy savings for mobile, consumer, enterprise, eMobility and new energy markets.
Measuring only 85.3mm x 60.8mm x 28.9mm (150cc), the HyperJuice 100W is powerful enough to charge two
15” Macbooks simultaneously (via the 2x USB-C), with flexibility for two more mobile devices via the additional
two USB-A ports.
“We wanted to make the smallest, most flexible 100W charger ever, so the circuit board and components are
laid out in the most compact and space-efficient manner using only the industry’s most efficient components
that can deliver the best performance,” says Daniel Chin, CEO of HYPER by Sanho Corporation. “GaNFast
technology enables 45% lower energy loss than the old, slow silicon chargers in the market today, and for the
ultimate in portability, at only 208g, it’s 50% lighter than competition too,” he adds.
The HyperJuice 100W uses power-sharing technology to deliver optimal charging to a vast array of multiple
devices, from watches and air-pod chargers all the way to a single 100W for the new Apple 16” Macbook. Either
of the two USB-C outputs can deliver the maximum 100W as specified by the USB Power Delivery (PD)
specification, with the two USB-A sockets providing up to 18W each for lower power, quick-charge or legacy
systems. Capable of worldwide AC voltage input, the HyperJuice is supplied with ‘snap-fit’ AC adapters (UK,
EU/Korea, AU) to support the international explorer and business traveler without additional bulky, heavy
converters.
“As shown by the $1.5m Kickstarter backing, confidence in the 100W HyperJuice is extremely high,” comments
Navitas’ CEO Gene Sheridan.
OPTOELECTRONICS
Indium gallium nitride surface-emitting superluminescent light diodes SemiconductorToday
Ireland’s Tyndall National Institute claims a record high 2.2W for output power from indium gallium nitride
(InGaN) superluminescent light-emitting diodes (SLEDs) [R. Cahill et al, Appl. Phys. Lett., vol115, p171102, 2019].
The researchers used slanted facets to direct the amplified spontaneous emission (ASE) through the GaN
substrate with very low feedback, avoiding laser action. The team also claims that their device is the first
surface-emitting structure, since previous reports used edge-emitting geometries.
GaNEX | III-N Technology Newsletter No. 83 | 60
The team comments: “The surface emitting structure provides potential for integration of further functionality
onto the back side of the device, increasing its potential for fiber-based systems and displays.” Other potential
uses include high-resolution optical coherence tomography, compact image projectors and smart solid-state
lighting.
SLEDs combine the operating principles of LEDs and laser diodes. Lasers generally use Fabry-Perot reflecting
structures to feedback light and boost stimulated emission. SLEDs use stimulated emission in a one-pass
structure to amplify spontaneously generated photons. The light from SLEDs benefits from features such as high
power output and high directionality. A number of strategies are used to suppress feedback, such as absorbing
facets or bent cavities.
Figure 1: Epitaxial structure.
The Tyndall InGaN material heterostructure was grown on n-GaN substrates using metal-organic vapor phase
epitaxy (Figure 1). The fabricated device (Figure 2) consisted of a 3μm-wide waveguide with 1mm gain length.
The etched end facets of the waveguide were angled at 45° to form turning mirrors, directing the emitted
radiation through the substrate. The back-side of the GaN substrate was polished to minimize scattering of the
radiation. A further measure to reduce feedback and increase light extraction was to apply a silicon dioxide anti-
reflective layer to the substrate surface.
Figure 2: Schematic of blue surface-emitting LED.
The device was operated with 220ns pulses and 1% duty cycle (Figure 3). The maximum output power of 2.2W
was achieved at 1.5A injection (50kA/cm2 density). The forward voltage was between 6V and 7V. The external
quantum efficiency at the maximum power was 49%. The peak wavelength occurred at 416nm. The researchers
GaNEX | III-N Technology Newsletter No. 83 | 61
comment: “The devices were not observed to degrade under these conditions, testament to the quality of the
low-defect-density substrate.”
Figure 3: Light–current-voltage and gain characteristics of blue SLED under pulsed operation.
Theoretical analysis using a standard gain model suggested that higher powers could be achieved in future. “The
peak optical powers provided by this device are far higher than has been previously reported,” the team writes.
The group attributes the high power to the technique for avoiding feedback: directing the radiation through the
substrate, rather than using absorbing back facets, for example.
The onset of amplified spontaneous emission occurs for an injection current of about 300mA. At lower current
the full-width at half maximum (FWHM) was around 26nm in wavelength. This decreased to the order of 6nm
(corresponding to a 41meV energy spread) above 300mA. FWHM values for InGaN lasers tend to be less than
1nm.
The anti-reflective coating was found to suppress parasitic lasing. In devices without such coating, evidence of
laser action occurred above 700mA injection.
Analysis of spontaneous emission from the top side of the device suggested active-region heating of the order of
110K between 300mA and 1.5A injection. Also, the study suggested that the carrier temperature increased by
about 100K between threshold and maximum power.
Increasing the pulse duration up to 1500ns reduced the output power (~20%) and increased the peak
wavelength slightly, indicating the effects of junction heating on the device. The researchers hope that improved
thermal management measurements could lead to longer pulse lengths or even continuous-wave operation at
higher currents.
Improving metal-organic growth of aluminium nitride on silicon carbide SemiconductorToday
University of California Santa Barbara (UCSB) in the USA have improved metal-organic chemical vapor
deposition (MOCVD) aluminium nitride (AlN) growth on silicon carbide (SiC) with a view to aluminium gallium
nitride (AlGaN) deep-ultraviolet light-emitting diode (DUV LED) and optoelectronics fabrication [Christian J.
Zollner et al, Appl. Phys. Lett., vol115, p161101, 2019].
GaNEX | III-N Technology Newsletter No. 83 | 62
The work was aimed at providing crack-free AlN templates for AlGaN growth with low threading dislocation
density without using costly and time-consuming approaches such as pulsed lateral overgrowth or growing very
thick (>10μm) buffer layers.
The researchers comment: “Combining overall improvements in AlN MOCVD techniques, improved SiC wafer
quality, and growth-mode control concepts demonstrated in molecular beam epitaxy (MBE), we find that
MOCVD growth of AlN/SiC is a viable route to high-quality UV-LED template layers.”
The team also points out that there are highly selective dry etch techniques for efficient SiC substrate removal,
raising the prospect of high-efficiency deep-UV LED fabrication. Such removal would be necessary for sub-
300nm deep-UV wavelengths that include the UV-C 260nm-285nm range, since SiC is highly absorbing of these
high-energy photons. In fact, SiC becomes absorbing around 380nm. UV-C LEDs could be used to kill bacterial
and viral pathogens in air, water, and on surfaces.
AlN can also be grown on much lower-cost sapphire, which is transparent to deep UV. The advantage of SiC is
that it is a much better match in terms of crystal structure. The researchers also point out that “there is no risk
of inadvertent nitrogen-polar growth on the substrate’s Si-face.”
At present, deep-UV LEDs exhibit low wall-plug efficiency due to a number on factors, one of which is the
presence of threading dislocations that direct electric energy into non-radiative recombination processes.
The UCSB MOCVD used trimethyl-aluminium and ammonia precursors as the sources of the aluminium and
nitrogen, respectively. A 250nm AlN initiation layer was grown at 1200°C, followed by 2.7μm AlN at 1400°C. The
growth rates were 1.5Å/s and 6Å/s, respectively. The two-step process targeted reduced numbers of threading
dislocations and a smoother surface.
Figure 1: Symmetric triple-axis 2ω-θ x-ray diffraction scans of AlN/SiC films, with SiC double-peak (blue) for
reference. Growth sequence with (black) and without (orange) ammonia pretreatment compared up to 75nm,
along with full 2.95μm AlN thickness template (black). Logarithmic intensity scale.
GaNEX | III-N Technology Newsletter No. 83 | 63
The 4H SiC substrates came from two suppliers. The ‘sample A’ substrate was mechanically polished with
polishing marks obscuring the atomic steps typically produced during the crystal growth process. In ‘sample B’,
which had a smoother surface from chemical-mechanical planarization (CMP), these steps were visible in
terraced surface structures. Samples A and B were 250μm and 500μm thick, respectively.
AlN films grown on sample B were found to have reduced tensile stress and less cracking. “The marked
reduction in tension when switching to smooth substrates suggests that small island size is a primary driver of
stress generation on rough substrates,” the team comments.
A 10 minute ammonia pretreatment of sample B at 1400°C for 10 minutes changed the slight tensile stress to
strong compression with a value of -1.1GPa. The surface was also crack-free up to a 5μm scale. X-ray rocking
curves also showed reduced full-width at half-maximum (FWHM) diffraction peaks, suggesting higher film
quality (Figure 1).
One effect of the pretreatment was to increase the spacing of the atomic steps from 165nm to 330nm. The
shorter step distance in the initial surface has been found to increase threading dislocation density and to create
lattice stacking mismatch problems.
Figure 2: In-situ curvature of AlN template on three substrate types: rough SiC with ammonia pretreatment
(top, tensile), smooth substrate (middle, weakly tensile), and smooth substrate with ammonia treatment
(bottom, highly compressive). Growth stress and 20-21 FWHM, Δω, listed. Inset: thermal expansion mismatch
stress: data (gray) compared with literature models (red, dashed) and linear least squares fit (black, solid).
Laser monitoring of the substrate curvature during growth (Figure 2) suggested a thermal expansion coefficient
mismatch in sample B of 1.13x10-6/°C, which resulted in a slight lattice mismatch increase of 0.15% at 1375°C. A
thick AlN layer is fully relaxed at its growth temperature, but on cooling to room temperature develops tensile
stress ~700MPa that can lead to cracking.
Plan-view transmission electron microscopy gave a threading dislocation density value of 2.4x108/cm2.
GaNEX | III-N Technology Newsletter No. 83 | 64
SUEZ and AquiSense partner on UV-C LED water disinfection for point-of-use laboratory applications SemiconductorToday
ikkiso Group company AquiSense Technologies LLC of Erlanger, KY, USA (which designs and manufactures water,
air and surface disinfection systems based on UV-C LEDs) has announced a unique product for SUEZ, which
manufactures water purification solutions for the healthcare, laboratory and scientific research sectors. The
partnership provides SUEZ with AquiSense’s patented ultraviolet light-emitting diode (UV-C LED) water
treatment technology for water disinfection directly at the point of use in critical laboratory applications.
AquiSense and SUEZ have been cooperating for over a year in a joint development effort to deliver a laboratory
water purification unit equipped with UV-C LED technology. The new product offers a high-level microbial
disinfection barrier directly at the point of use. Unlike competing units, where pathogens can enter the
upstream pipeline contaminating the system and future samples, the new UV LED disinfection acts as a barrier
preventing contamination from entering the water purification system as a whole.
“This partnership signifies an adaptation of the UV LED technology in the more critical fields of healthcare and
research,” says AquiSense’s European sales director Thomas Arnold.
“The new system developed by SUEZ eliminates recontamination problems by using LED lamps located within
the dispense head, at the point of use,” says SUEZ’s innovation engineer John Higgs. “This is the first time such
technology has been used in this way and brings a number of further important benefits.”
Plessey develops native red InGaN LEDs on silicon for micro-LED displays SemiconductorToday
Plessey of Plymouth, UK, which develops embedded micro-LED technology for augmented-reality and mixed-
reality (AR/MR) display applications, has developed what it claims is the first gallium nitride on silicon (GaN-on-
Si)-based red LED.
While indium gallium nitride (InGaN)-based blue and green LEDs are commercially available, red LEDs are
typically based on aluminium indium gallium phosphide (AlInGaP) material or color-converted red LEDs. For
augmented-reality applications, achieving high-efficiency ultra-fine-pitch red pixels (<5µm) remains elusive due
to severe edge effects from AlInGaP material and cavity losses from color-conversion processes.
InGaN-based red LEDs offer lower manufacturing costs, scalability to larger 200mm- or 300mm-diameter wafers
and better hot/cold factor over incumbent AlInGaP-based red LEDs. However, achieving red spectral emission
with InGaN material is challenging due to the high indium content inducing significant strain in the active region,
GaNEX | III-N Technology Newsletter No. 83 | 65
subsequently reducing crystal quality and creating numerous defects. Plessey says that it has overcome these
challenges by using a proprietary strain-engineered active region to create an efficient InGaN red LED.
Plessey’s InGaN red micro-LEDs have a wavelength of 630nm at an injection current density of 10A/cm2, a full
width at half maximum (FWHM) of 50nm, hot/cold factor over 90% and higher efficiencies over conventional
AlInGaP and color-converted red LEDs at ultra-fine pixel pitches. With this result, Plessey now has the capability
to manufacture native blue, green and red InGaN material or to tune wavelengths from 400nm to 650nm using
its GaN-on-Si platform.
“It creates a path towards low-cost manufacturing of ultra-fine-pitch and efficient red InGaN pixels, which will
accelerate the adoption of micro-LEDs in both AR micro-displays and mobile/large display applications,” says Dr
Wei Sin Tan, Plessey’s director of Epitaxy and Advanced Product Development.
Other recent milestones from Plessey include what is claimed to be the first wafer-level bonded monolithic
3000ppi (pixel-per-inch) GaN-on-Si micro-LED emissive display hybridized to an active-matrix CMOS backplane,
as well as native blue and green emission layers on the same wafer. Plessey is continuing to rapidly develop
micro-LED display solutions, with its roadmap including the production of full-RGB micro-LED displays in 2020.
Plessey is exhibiting in booth #21861 (South Hall 1) at the 2020 Consumer Electronics Show (CES) in the Las
Vegas Convention Center (7–10 January). The firm is joining forces with Compound Photonics of Vancouver, WA,
USA (a provider of compact high-resolution micro-display technologies for AR/MR applications) to develop what
is reckoned to be the smallest 1080p micro-LED-based near-eye display solution for AR/MR applications.
Demonstrated at CES will be active-matrix displays in both native blue and green; as well as the new direct-drive
display with the first-generation development kit. The technology is being showcased within an head-mounted
display (HMD) head-up display (HUD) projection system.
OTHER
University of Illinois reports thermal conductivity dependence on dislocation density of various GaN materials SemiconductorToday
Gallium nitride (GaN) materials are critical for energy conversion, communications and sensing but, despite
material advantages, existing mainstream GaN photonic and electronic devices are limited by the thermal heat
GaNEX | III-N Technology Newsletter No. 83 | 66
extraction, and one of the biggest challenges in GaN devices (including RF transistors and LEDs) is heat
extraction.
A research team at the University of Illinois at Urbana-Champaign (UIUC) led by professor Can Bayram has now
reported what is clamed to be the first systematic study of the thermal conductivity of gallium nitride materials
with various dislocation densities, including hydride vapor phase epitaxy (HVPE)-grown GaN, high nitride
pressure (HNP)-grown GaN, and metal-organic chemical vapor deposition (MOCVD)-grown GaN on sapphire
(GaN/sapphire) and on silicon (111) (GaN/Si) – see K. Park and C. Bayram, ‘Impact of dislocations on the thermal
conductivity of gallium nitride studied by time-domain thermoreflectance’, J. Appl. Phys. 126, 185103 (2019).
GaN thermal conductivities (κGaN) of HVPE GaN, HNP GaN and MOCVD-grown GaN/sapphire and GaN/Si are
measured as 204.7(±4.6), 206.6(±6.8), 191.5(±10.5) and 164.4(±3.2)W/m.K, respectively, using time-domain
thermoreflectance (TDTR). Dislocation densities (σD) of HVPE GaN, HNP GaN, GaN/sapphire, and GaN/Si are
measured as 4.80(±0.42)x105, 3.81(±0.08)x106, 2.43(±0.20)x108 and 1.10(±0.10)x109cm-2, respectively, using
cathodoluminescence and XRD. Impurity concentrations of Si, H, C and O are measured by secondary-ion mass
spectroscopy (SIMS) to complement the analysis.
Graphic: Effect on thermal conductivity of dislocation density in various GaN materials. κGaN of HVPE GaN,
HNP GaN, GaN/sapphire and GaN/Si as a function of σD (open symbols). Empirical model by Mion et al [Appl.
Phys. Lett. 89, 092123 (2006)], κGaN = 230tanh0.12(5×106/σD) (dotted line), new empirical model, κGaN =
210 tanh0.12(1.5×108/σD) (dashed line, University of Illinois work), and modified Klemens’ model (solid line,
University of Illinois work) are plotted together for comparison.
Using the experimental data, the team proposes a new empirical model to describe how thermal conductivity of
GaN is affected by dislocation density, specifically κGaN = 210tanh0.12(1.5x108/σD). They also propose a
GaNEX | III-N Technology Newsletter No. 83 | 67
modification in Klemens’ model, where dislocation-induced scattering strength is increased, to explain the
experimental rate of decrease in thermal conductivity with increasing dislocation density.
Their empirical expression provides a means to estimate the thermal conductivity of heteroepitaxially grown
GaN samples indirectly by determining the dislocation density which is, in many cases, simpler than directly
measuring the thermal conductivity.
The team reckons that the work provides key design guidelines for the thermal management of GaN-based
devices, typically grown on foreign substrates with high dislocation densities.
Veeco’s revenue rebounds in Q3 as 300mm GaN MOCVD cluster system accepted for pilot production SemiconductorToday
For third-quarter 2019, epitaxial deposition and process equipment maker Veeco Instruments Inc of Plainview,
NY, USA has reported revenue of $109m, down 14% on $126.8m a year ago but up 11.5% on $97.8m last
quarter and above the midpoint of the $95-115m guidance range.
The LED Lighting, Display & Compound Semiconductor segment – which includes photonics, 5G RF, power
devices and advanced display applications – contributed $24m (22% of overall revenue), more than doubling
from just $10m last quarter, including service and upgrades for LED customers and shipment of Veeco’s first
300mm fully automated single-wafer gallium nitride (GaN) metal-organic chemical vapor deposition (MOCVD)
cluster system to a “leading-edge semiconductor fab” for a pilot-production environment (after completing
development during the quarter). “We recently obtained acceptance from our customer on this tool,” notes
CEO Bill Miller.
The Front-End Semiconductor segment (formerly part of the Scientific & Industrial segment, before the May
2017 acquisition of lithography, laser-processing and inspection system maker Ultratech Inc of San Jose, CA,
USA) contributed $34m (31% of total revenue), up 36% on $25m last quarter, driven by shipment of Veeco’s
second production extreme ultraviolet (EUV) mask blank system as well as sales of multiple laser spike annealing
(LSA) systems. Also, shipments to data storage customers remained solid as they continued to invest in
technology and capacity.
The Advanced Packaging, MEMS & RF Filter segment – including lithography and Precision Surface Processing
(PSP) systems sold to integrated device manufacturers (IDMs) and outsourced assembly & test firms (OSATs) for
Advanced Packaging in automotive, memory and other areas – contributed $11m (10% of overall revenue),
falling 31% from $16m last quarter, reflecting continued market softness.
The Scientific & Industrial segment fell back by 15% from $47m last quarter to $40m (37% of total revenue),
including ion beam system shipments to data storage customers as well as sales of ion beam sputtering systems
to high-end optical coating customers.
Read more
GaN substrate market to grow at 10% CAGR to 2027 SemiconductorToday
In terms of revenue, the global gallium nitride (GaN) substrate market will expand at a compound annual growth
rate (CAGR) of ~10% to $225m in 2027, estimates a report by Transparency Market Research.
GaNEX | III-N Technology Newsletter No. 83 | 68
GaN substrates promise to dramatically enhance the performance, efficiency and ubiquity of sophisticated
power management and control functions. If low-cost bulk GaN substrate is not available, GaN can be grown on
other substrates such as sapphire, silicon carbide (SiC) or silicon. For better cost economics, GaN devices can be
fabricated on large-diameter silicon substrates in existing silicon CMOS (complementary metal-oxide-
semiconductor) fabs. GaN devices are gaining popularity due to various advantages that they offer including
high breakdown voltage, high switching speed, high thermal conductivity and low on-resistance. This is expected
to have a positive impact on the gallium nitride substrate market.
GaN substrates have evolved
significantly since their
introduction a few years ago. The
growing use of GaN technology
devices for high-frequency, high-
voltage, and high-temperature
applications is expected to drive
the global GaN substrate market
during the forecast period.
Increasing adoption of white-light
LEDs is another factor boosting the
GaN substrate market. GaN
substrates are increasingly being
used to make white-light LEDs, in
addition to power devices, that
exceed the performance of current
devices, as they offer improved electric characteristics. Furthermore, rapid advances in GaN technology have led
to the development of efficient GaN substrates with low defect density and free macro defect density. Hence,
they can increasingly be used for realizing white-light LEDs. The increasing adoption of white-light LEDs is hence
expected to drive growth of the GaN substrate market.
Asia-Paciffic region to remain dominant
Having accounted for a key share of the global GaN
substrate market in 2018, the Asia-Pacific region is
expected to continue to dominate between 2019
and 2027 due to the rising popularity of GaN
devices for various applications in several end-use
industries. China constituted a significant share of
the Asia-Pacific market in 2018, and the country
will see large investments in R&D, targeted at
innovating new technologies. Also, the region is
home to prominent GaN technology companies
that are engaged in R&D on innovative GaN
solutions and their introduction to the
marketplace.
North America has emerged as the second-largest
market for GaN substrates. The region is expected
to maintain a considerable share of the global
market during the forecast period, due to the
GaNEX | III-N Technology Newsletter No. 83 | 69
increasing adoption of GaN substrates for various applications such as white-light LEDs and the increasing
adoption of electric vehicles. GaN-based devices and GaN substrates can be employed in several applications in
the automotive sector, such as LiDAR, 48V–12V power distribution, and high-intensity headlights. The region
therefore presents significant opportunities for the GaN substrate market, the report reckons.
Europe is expected to be a lucrative market for GaN substrates throughout the forecast period due to the
growing popularity of GaN devices and their rising use in the automotive industry in countries in Western
Europe and Central Europe. The European market is anticipated to increase in the next few years due to rapid
industrialization in the region. Furthermore, key players are engaged in making technical advances in GaN
technology to overcome the challenges associated with devices based on this technology.
Key players in the global GaN substrate market are displaying synergies through close cooperation and
collaboration in sales, marketing and technical advances. GaN substrate suppliers are also expanding by forming
strategic alliances with peers as well as various research institutions in order to establish themselves as players
in the global market.
Boost to magnesium doping of gallium nitride on freestanding substrates SemiconductorToday
Japan’s National Institute for Materials Science (NIMS) has found that magnesium doping of gallium nitride
(GaN:Mg) is far more effective in material grown homoepitaxially on freestanding substrates as opposed to
GaN/sapphire templates [Liwen Sang et al, Appl. Phys. Lett., vol115, p172103, 2019].
The researchers point to the reduction of self-compensation as the basis for the enhanced doping performance.
Self-compensation occurs where acceptor states are neutralized by the generation of parasitic deep-donor non-
radiative recombination centers (NRCs). Also, the reduced numbers of threading dislocations in material grown
on freestanding substrates is thought to reduce Mg diffusion effects that adversely affect doping performance.
Freestanding substrates can have threading dislocation densities as low as 104/cm2, some three orders of
magnitude lower than for GaN/sapphire templates. Of course, freestanding substrates are significantly more
expensive than the templates, but the development of potential application opportunities and substrate
production technology should encourage economies of scale in future.
The enhanced GaN:Mg on freestanding substrates was found to have five to ten times the free hole density,
implying higher conductivity. In addition, one would expect higher mobility if lower magnesium concentration
can be used due to reduced impurity scattering.
Another potential use of p-GaN is as a current-blocking layer in vertical metal-oxide-semiconductor field-effect
transistors (MOSFETs) and current-aperture vertical electron transistors (CAVETs). The creation of p-GaN:Mg
during epitaxial growth is preferred over ion implantation. The latter process suffers from excessive out-
diffusion of the dopants during thermal anneal processes.
Metal-organic chemical vapor deposition (MOCVD) was used to grown 1μm Mg-doped GaN on c-plane n+-GaN
freestanding substrates with 4x106/cm2 threading dislocation density. The growth temperature was 1000°C and
bis(methylcyclopentadienyl) magnesium was the precursor for the doping. The Mg-doped layer was grown on
an undoped 2μm GaN buffer with 5x1015/cm3 free electron density. The Mg doping was activated with 30-
minute annealing at 725-820°C.
GaNEX | III-N Technology Newsletter No. 83 | 70
One effect of using GaN substrates was narrow peaks in x-ray diffraction (XRD) rocking curves (Figure 1):
68arcsec full-width at half maximum (FWHM) for the (002) plane and 95arcsec for (102). These values
correspond to a threading dislocation density of 7x106/cm2. The same growth process, but using GaN/sapphire
templates, led to FWHM values of 280arcsec and 491arcsec for the (002) and (102) planes, respectively. The
estimated threading dislocation density in this case was 6x109/cm2, almost three orders of magnitude higher
than for the GaN:Mg on freestanding substrate.
Figure 1: (left) XRD omega rocking curves of (002)- and (102)-plane reflection for homoepitaxial and
heteroepitaxial GaN:Mg films. (right) Free hole concentration and [Mg] values for homoepitaxial and
heteroepitaxial GaN:Mg films.
Hall measurements with lightly doped GaN on GaN/sapphire template with 1.4x1019/cm3 {Mg} concentration
gave a 6x1016/cm2 free hole density. Homoepitaxy on freestanding GaN increased the free hole concentration
five-fold to 3x1017/cm3 with a reduced {Mg} of 8x1018/cm3. The higher Mg incorporation on sapphire was
attributed to a higher density of edge-type dislocations.
Heavier Mg-doping resulted in free hole concentrations of 6.0x1017/cm3 on freestanding substrate (1.8x1019
Mg concentration). This was ten times the 6.1x1016/cm3 on sapphire for the same Mg flow. The team
comments: “The marked enhancement of the doping efficiency is attributed to the suppression of the Mg-
related self-compensation centers or non-radiative recombination centers benefitting from the greatly reduced
dislocation density.”
The researchers also found that the relation between photoluminescence (PL) spectral structure and p-type
conductivity in GaN:Mg was different on freestanding GaN substrates, compared with heteroepitaxy on
sapphire (Figure 2).
With heteroepitaxial GaN:Mg a blue-band luminescence (BL, ~2.9eV) is associated with onset of p-conductivity.
This luminescence is generally attributed to deep donor-acceptor pair (DAP) recombination.
By contrast the NIMS researchers found that ultraviolet luminescence (UVL, ~3.26eV) was the signal for
homoepitaxial GaN:Mg on freestanding GaN to be p-type conducting. These emissions were attributed to free
electron or shallow donor recombination with acceptor levels.
GaNEX | III-N Technology Newsletter No. 83 | 71
The PL spectra also include near-band-edge (NBE) emissions and yellow luminescence (YL). The YL emissions are
attributed to electron transitions into deep acceptor levels associated with carbon atoms on nitrogen sites.
Figure 2: PL spectra of p-GaN films grown on (a) GaN substrates and (b) GaN/sapphire templates activated at
725°C in N2 with different Mg doping concentrations. (c) and (d) PL spectra of homoepitaxial and
heteroepitaxial GaN:Mg films activated at varying temperatures, respectively.
The homoepitaxial GaN:Mg had increased ultraviolet luminescence with increased activation anneal
temperatures up to 750°C, but then BL emissions started appearing, indicating reduced effectiveness. The
higher activation temperatures also resulted in increased surface roughness measured using atomic force
microscopy: 0.81nm root mean square at 770°C, compared with 0.25nm at 725°C.
The NIMS team comments: “The rough morphology deteriorates the luminescence behaviors, which is related
to the increased thermal emission of electrons from donor levels to the conduction band and their recapture by
the non-radiative recombination centers on the rougher surface. The electrical current of Ohmic contacts is
reduced when the activation temperature is higher than 750°C.”
X-ray photoelectron spectra (XPS) indicated that homoepitaxy also improved the uniformity of surface states,
avoiding regions with excess Mg-Ga-O. Such excess Mg-Ga-O inhibits abrupt interfaces when growing aluminium
GaNEX | III-N Technology Newsletter No. 83 | 72
oxide dielectric. Abrupt interfaces are desired for metal-oxide-semiconductor structures in vertical field-effect
transistors with high mobility and stable positive threshold voltages.
Electrochemical membrane release for aluminium gallium nitride devices SemiconductorToday
Researchers in Sweden and Germany have been developing electrochemical etching as a means to create thin-
film aluminium gallium nitride (AlGaN) optoelectronic and power-electronic devices [Michael A. Bergmann et al,
Appl. Phys. Lett., vol115, p182103 2019]. AlGaN alloys are wide-bandgap materials with the potential for deep
ultraviolet (UV) light emission and for electronics that can sustain high electric fields and voltages before
breakdown.
The researchers at Sweden’s Chalmers University of Technology, Germany’s Technische Universität Berlin and
Sweden’s KTH Royal Institute of Technology comment: “Heterogeneously integrated AlGaN epitaxial layers will
be essential for future optical and electrical devices like thin-film flip-chip ultraviolet light-emitting diodes, UV
vertical-cavity surface-emitting lasers, and high-electron-mobility transistors on efficient heat sinks. Such AlGaN
membranes will also enable flexible and micromechanical devices.”
Releasing the AlGaN layers from the epitaxial growth substrate would enable vertical cavities with dielectric
applied to both sides of a membrane. For high-power electronics, thin-film formats would allow better thermal
management by applying the active semiconductor layers directly to heatsinks. However, present methods for
releasing AlGaN such as laser lift-off tend to damage the material, reducing performance in the final device.
Figure 1: (a) AlGaN sample structure, (b) three-electrode setup for electrochemical etching, and (c) etching
current versus time for etching Al0.11Ga0.89N sacrificial layer at 30V.
The researchers first grew a 2x1018/cm3 silicon-doped Al0.5Ga0.5N layer on c-plane sapphire with an AlN
template layer using a close-coupled showerhead metal-organic chemical vapor deposition (MOCVD) reactor
(Figure 1). The n-type conductivity from the silicon doping ensured current spreading for uniform
electrochemical etching.
The current-spreading layer was followed by a 225nm 0.5x1018/cm3 {Si] lightly doped Al0.5Ga0.5N etch-stop
layer. The sacrificial layer for membrane release was 130nm 2x1019/cm3 heavily Si-doped AlxGa1-xN. The
membrane layer was 580nm (1900nm for Al0.11Ga0.89N sacrificial layer sample) unintentionally doped
Al0.5Ga0.5N.
X-ray analysis showed that the Al0.5Ga0.5:Si was ‘pseudomorphic’ - i.e. strained – on all sacrificial layer
compositions.
GaNEX | III-N Technology Newsletter No. 83 | 73
The electrochemical etching was enabled by dry reactive-ion etching 10μm-diameter via holes in a 7x9 400μm
pitch array to expose the sacrificial layer. The etched holes reached down to the current-spreading layer. The
electrochemical contact with the current-spreading layer was made through an electron-beam evaporated and
annealed vanadium/aluminium/vanadium/gold metal stack. The top-side of the membrane was protected from
etching damage with a 1.3μm photoresist layer.
The electrochemical etch used three electrodes in 0.3M nitric acid electrolyte, which was constantly stirred with
a magnetic bar. The AlGaN ‘working electrode’ was kept at a constant positive potential relative to the
silver/silver chloride (Ag/AgCl) ‘reference electrode’. Control of the process was through a graphite rod ‘counter
electrode’, which allowed the current flow to vary in the low milliamp range. The samples were 5mmx10mm.
The electrochemical etch was found to proceed isotropically around the etch holes, creating an air gap between
the substrate and membrane. Eventually the etch fronts merge. With an Al0.5Ga0.5N sacrificial layer, an etch
potential of 30V resulted in smooth surfaces on the upper and lower etch-stop layers. At the lower potential of
25V some residues were left on the etch-stop layers. Even lower potentials, of 20V and 15V, resulted in
increasingly porous sacrificial layers.
Figure 2: (a) As-grown MQW sample structure, (b) transferred MQW-containing structure, (c) PL spectrum of
as-grown MQW probed from Ga-polar side and transferred structure probed from etched N-polar side, and
(d) time-resolved PL of structures.
The researchers attribute the etching to the generation of holes at AlGaN/electrolyte interface from Zener
tunneling or avalanche breakdown in a depletion region. “These holes oxidize AlGaN at the interface, and the
GaNEX | III-N Technology Newsletter No. 83 | 74
oxidized material can be dissolved by the electrolyte,” the team explains. The researchers propose a chemical
reaction equation:
2AlxGa1-xN + 6h+ → 2xAl3+ + 2(1-x)Ga3+ + N2
Atomic force microscopy on the etched surface of a membrane transferred to a silicon carrier had 3.5nm root-
mean-square (RMS) roughness on a 1μmx1μm area. The sacrificial layer used for the electrochemical etch was
Al0.27Ga0.73N.
A multiple quantum well (MQW) structure was grown on a 130nm Al0.37Ga0.63N sacrificial layer to show that
the electrochemical etch could be used without affecting device performance (Figure 2). The 2x1018/cm3 {Si]
Al0.5Ga0.5N 4μm-thick underlayer was relaxed. The sacrificial layer aluminium content was chosen to be
transparent for photoluminescence (PL) analysis but low enough to contrast with the surrounding layers.
The MQWs were indium aluminium gallium nitride with 21% Al content. The three wells were 2nm thick,
separated by 5nm Al0.3Ga0.7 barriers. The magnesium-doped p-type layers were an Al0.75Ga0.25N electron-
blocking layer, an AlGaN superlattice (SL), and a 20nm p-GaN cap.
The material was prepared for electrochemical etching by dry reactive-ion etching circular mesas. Palladium was
deposited on the p-GaN cap. The mesas were partially covered with 1μm sputtered silicon dioxide (SiO2) to
prevent parasitic etching during the electrochemical process. Finally, a titanium/gold bond pad was deposited
on the palladium.
The electrochemical etch potential was 25V. The released structures were transferred to silicon carriers with
titanium/gold bonding layer using a 300°C thermos-compression process.
The PL analysis showed a small red-shift after transfer. The researchers report “This shift of 2nm could be
caused by small local variations in the Al-composition and thickness over the sample, residual strain in the
epitaxy, and process-induced strain.”
Time-resolved measurements before and after transfer showed the same PL decay rate of 340ps. The team
concludes: “This confirms that the electrochemical etching and transfer process do not influence the quality of
the QWs and, hence, are an appropriate process for fabrication of devices based on free-standing membranes.”
Panasonic to sell its chip unit to Taiwan's Nuvoton for $250 million Reuters
TOKYO (Reuters) - Panasonic Corp (6752.T) said it would sell its loss-making semiconductor unit to Taiwan’s
Nuvoton Technology Corp (4919.TW) for $250 million as the Japanese electronics giant struggles to lift its profit
amid a lack of growth drivers.
The sale is part of Panasonic’s plans to cut fixed costs by 100 billion yen ($920 million) by the year ending in
March 2022 by consolidating production sites and overhauling loss-making businesses.
Panasonic has already divested most of its chip business as it lost to more nimble Korean and Taiwanese rivals,
and has shut down or shifted its manufacturing facilities to its joint venture (JV) with Israel’s Tower
Semiconductor (TSEM.TA).
GaNEX | III-N Technology Newsletter No. 83 | 75
Its semiconductor unit currently focuses on designing power-management chips and sensors for smartphones,
cars and security cameras. It sold part of the power management chip business to Japan’s Rohm Co (6963.T) this
month.
The latest deal includes the sale of the entire JV, which is owned 51% by Tower and 49% by the Panasonic chip
unit. The JV operates three Japanese chipmaking facilities.
Panasonic said the sale will not have any significant impact on its earnings. The value of the deal that Panasonic
has announced excludes the amount Nuvoton would pay for Tower Semiconductor’s stake in the joint venture.
Nuvoton said in a statement the all-cash transaction was expected to close by June 2020, and would “increase
Nuvoton’s presence in the global semiconductor industry through greater scale and volume of semiconductor
solutions”.
Nuvoton, which was spun off from Winbond Electronics Corp (2344.TW) in 2008, supplies chips for electronic
devices including computers and audio products.
GaNEX | III-N Technology Newsletter No. 83 | 76
PATENT APPLICATIONS
More than 290+ new patent families (inventions) were published in November 2019.
Other patent applicants Asahi Kasei, Chip Foundation Technology, East China Normal University, Exagan, Fujian Prima Optoelectronics, Guangdong Institute of Semiconductor Industrial Technology, Guangdong University of Technology, HC Semitek, Institute of Semiconductors, Jiangsu Ji Cai Intelligent Sensing Technology Research Institute, Julicheng Semiconductor, Meijo University, Nanjing University of Science & Technology, Nuodinghan Intelligent Electrification Research Institute, Osram Opto Semiconductors, Purdue Research Foundation, Qualcomm, Seoul Viosys, Shandong Inspur Huaguang Optoelectronics, Shanghai Huali Microelectronics, Shenzhen Jing Xiang Technologies, Sun Yat Sen University, Suzhou Institute of Nano Technology & Nano Bionics Chinese Academy of Sciences, Suzhou Institute of Nano Technology & Nano Bionics Sinano Chinese Academy of Sciences, Taiwan Semiconductor Manufacturing, University of Colorado, University South Science & Technology China, Wuhan University, Wuhu Qidi Semiconductor, Xi An Keruisheng Innovative Technology, Xiamen Changelight, 3D Floor No 6 Industrial Six Road Pingzhen Industrial Zone Taoyuan City China, ABB Schweiz, Ames Micron, Analog Foundries, Ascatron, Beijing Bozhong Yiyou Technology, Black Peak, Cambridge Enterprise, Cas Spectra Technology, Central South University, Changshaniumidrivetechnologyco, Chunghwa Precision Test Technology, Columbia University, Dalian University of Technology, Delta Electronic Enterprise Management, Dongguan Institute of Opto Electronics Peking University, Ecole Polytechnique Federale De Lausanne (EPFL), Elux, Enkris Semiconductor, Ericsson, ETRA Semiconductor, First Affiliated Hospital of Medical College of Xi An Jiaotong University, Foshan Guoxing Semiconductor Technology, Fuji Electric, General Interface Solution, GIS Technology, Gree Electric Appliances, Guangdong APT Electronics, Guangdong Electronic Information Engineering Research Institute of UESTC, Guangdong Fenghua Advanced Technology Holding, Guangdong Fenghua Core Power Technology, Guangdong Juhua Printed Display Technology, Guangwei Integration Technology, Guangxi Subtropical Crops Research Institute, Gwangju Institute of Science & Technology, Haidike Photoelectric Science & Technology, Harbin Institute of Technology, Hebei Yongsheng Foodstuff, Hengshan Jiacheng New Material, Hosei University, Huaiyin Teachers College, Huangshan Ruixing Automobile Electronic System, Hyperfine Research, Imec;
GaNEX | III-N Technology Newsletter No. 83 | 77
Notable new patent applications
Enhancement-mode high-electron-mobility transistor Publication Number: WO2019/224448 Patent Applicant: EXAGAN
The invention relates to an enhancement-mode high-electron-mobility transistor comprising: • a structure (10) including a stack (1) made of III-V semiconductor materials defining an interface (2) and capable of forming a conduction layer (3) in the form of a two-dimensional electron-gas layer; • a source electrode (20) and a drain electrode (30) forming an electrical contact with the conduction layer (3); and • a gate electrode (40) arranged on top of the structure (10), between the source electrode (20) and the drain electrode (30). The structure (10) comprises a bar (4) that is arranged below the gate electrode (40) and passes through the interface (2) of the stack (1). Said bar (4) comprises two semiconductor portions exhibiting opposite types of doping, defining a p-n junction in proximity to the interface (2).
Micro light-emitting diode display fabrication and assembly Publication Number: US20190363069, WO2019/226255 Patent Applicant: INTEL
Micro light-emitting diode (LED) displays, and fabrication and assembly of micro LED displays, are described. In an example, a pixel element for a micro-light emitting diode (LED) display panel includes a blue color nanowire or nanopyramid LED above a first nucleation layer above a substrate, the blue color nanowire or nanopyramid LED including a first GaN core. A green color nanowire or nanopyramid LED is above a second nucleation layer above the substrate, the green color nanowire or nanopyramid LED including a second GaN core. A red color nanowire or nanopyramid LED is above a third nucleation layer above the substrate, the red color nanowire or nanopyramid LED including a GaInP core.
GaNEX | III-N Technology Newsletter No. 83 | 78
Pixel architectures for low power micro light-emitting diode displays Publication Number: WO2019/226246 Patent Applicant: INTEL
Pixel architectures for low power micro light-emitting diode displays are described. In an example, a micro light emitting diode pixel structure includes a substrate having a plurality of conductive interconnect structures in a first dielectric layer thereon. A plurality of micro light emitting diode devices is in a second dielectric layer above the first dielectric layer, individual ones of the plurality of micro light emitting diode devices electrically coupled to a corresponding one of the plurality of conductive interconnect structures. The plurality of micro light emitting diode devices includes an orange micro light emitting diode device, a green micro light emitting diode device, and a blue micro light emitting diode device. A transparent conducting oxide layer is disposed on the plurality of micro light emitting diode devices and on the second dielectric layer.
Photonic and electronic devices on a common layer Publication Number: WO2019/217141 Patent Applicant: RAYTHEON
Photonic devices having A11-xScxN and A1yGa1-yN materials, where A1 is Aluminum, Sc is Scandium, Ga is Gallium, and N is Nitrogen and where 0 is less than x and x is less than or equal to 0.45 and 0 is less than or equal to y and y is less than or equal to 1.
Method of dividing a bar of one or more devices Publication Number: WO2019/222669
Patent Applicant: UNIVERSITY OF CALIFORNIA
A method for dividing a bar of one or more devices. The bar is comprised of island-like III-nitride-based semiconductor layers grown on a substrate using a growth restrict mask; the island-like III-nitride-based semiconductor layers are removed from the substrate using an Epitaxial Lateral Overgrowth (ELO) method; and then the bar is divided into the one or more devices using a cleaving method.
GaNEX | III-N Technology Newsletter No. 83 | 79
Gallium-nitride-based transcaps for millimeter wave applications Publication Number: WO2019/226330, US20190363198 Patent Applicant: QUALCOMM
Certain aspects of the present disclosure provide a semiconductor variable capacitor. The semiconductor variable capacitor generally includes a first semiconductor region having a first doping type, a second semiconductor region having a second doping type different from the first doping type, a third semiconductor region disposed between the first semiconductor region and the second semiconductor region, a first terminal disposed adjacent to the first semiconductor region, a second terminal disposed adjacent to the second semiconductor region, and a third terminal disposed above the third semiconductor region. The first semiconductor region, the second semiconductor region, and/or the third semiconductor region include gallium nitride. The third semiconductor region includes multiple semiconductor layers having different materials. A capacitance between the first terminal and the third terminal is configured to be adjusted by varying a control voltage applied to at least one of the first terminal or the second terminal.
Enhanced doping efficiency of ultrawide bandgap semiconductors by metal-semiconductor assisted epitaxy Publication Number: WO2019/227100, US20190363218 Patent Applicant: UNIVERSITY OF MICHIGAN
An epitaxial growth process, referred to as metal-semiconductor junction assisted epitaxy, of ultrawide bandgap aluminum gallium nitride (AIGaN) is disclosed. The epitaxy of AIGaN is performed in metal-rich (e.g., Ga-rich) conditions using plasma- assisted molecular beam epitaxy. The excess Ga layer leads to the formation of a metal-semiconductor junction during the epitaxy of magnesium (Mg)-doped AIGaN, which pins the Fermi level away from the valence band at the growth front. The Fermi level position is decoupled from Mg-dopant incorporation; that is, the surface band bending allows the formation of a nearly n-type growth front despite p-type dopant incorporation. With controlled tuning of the Fermi level by an in-situ metal- semiconductor junction during epitaxy, efficient p-type conduction can be achieved for large bandgap AIGaN.
GaNEX | III-N Technology Newsletter No. 83 | 80
Implanted dopant activation for wide bandgap semiconductor electronics Publication Number: US20190341261, WO2019/213001 Patent Applicant: US NAVY
An enhanced symmetric multicycle rapid thermal annealing process for removing defects and activating implanted dopant impurities in a Ill-nitride semiconductor sample. A sample is placed in an enclosure and heated to a temperature T1 under an applied pressure P1 for a time t1. While the heating of the sample is maintained, the sample is subjected to a series of rapid laser irradiations under an applied pressure P2 and a baseline temperature T2. Each of the laser irradiations heats the sample to a temperature Tmax above its thermodynamic stability limit. After a predetermined number of temperature pulses or a predetermined period of time, the laser irradiations are stopped and the sample is brought to a temperature T3 and held at T3 for a time t3 to complete the annealing.
Formation of a III-N semiconductor structure Publication Number: US20190362967 Patent Applicant: IMEC
According to an aspect of the present disclosure, there is provided a III-N semiconductor structure comprising: a semiconductor-on-insulator substrate; a buffer structure comprising a superlattice including at least a first superlattice block and a second superlattice block formed on the first superlattice block, the first superlattice block including a repetitive sequence of first superlattice units, each first superlattice unit including a stack of layers of AlGaN, wherein adjacent layers of the stack have different aluminum content, the second superlattice block including a repetitive sequence of second superlattice units, each second superlattice unit including a stack of layers of AlGaN, wherein adjacent layers of the stack have different aluminum content, wherein an average aluminum content of the second superlattice block is greater than an average aluminum content of the first superlattice block; and a III-N semiconductor channel layer arranged on the buffer structure.
GaNEX | III-N Technology Newsletter No. 83 | 81
Method for fabricating a hybrid display using inorganic micro light emitting diodes (uleds) and organic leds (oleds) Publication Number: US20190355708 Patent Applicant: ELUX A hybrid light emitting diode (LED) display and fabrication method are provided. The method forms a stack of thin-film layers overlying a top surface of a substrate. The stack includes an LED control matrix and a plurality of pixels. Each pixel is made up of a first subpixel enabled using an inorganic micro LED (uLED), a second subpixel enabled using an organic LED (OLED), and a third subpixel enabled using an OLED. The first subpixel emits a blue color light, the second subpixel emits a red color light, and the third subpixel emits a green color light. In one aspect, the stack includes a plurality of wells in a top surface of the stack, populated by the LEDs. The uLEDs may be configured vertical structures with top and bottom electrical contacts, or surface mount top surface contacts. The uLEDs may also include posts for fluidic assembly orientation.
Nitride semiconductor light emitting element Publication Number: JP2019197857, CN110473943, US20190348569, EP3567643 Patent Applicant: PANASONIC A flip-chip light emitting diode element capable of reducing lateral resistance. The flip-chip light emitting diode element includes a stacked body structure configured by sequentially stacking a first n-type group III nitride semiconductor layer having a carrier concentration that is at least 1 × 1019cm-3but less than 3 × 1020cm-3, a second n-type group III nitride semiconductor layer having a carrier concentration that is at least 5 × 1017cm-3but less than 1 × 1019cm-3, a light-emitting layer formed by a group III nitride semiconductor, and a p-type group III nitride semiconductor layer. A height of unevenness on an interface between the first n-type group III nitride semiconductor layer and the second n-type group III nitride semiconductor layer is greater than that of unevenness of an interface between the second n-type group III nitride semiconductor layer and the light emitting layer.
Semiconductor element and method for manufacturing the same Publication Number: US20190355580, JP2019201158 Patent Applicant: TOSHIBA
According to one embodiment, a semiconductor element includes a first nitride semiconductor region, a second nitride semiconductor region, and an intermediate region provided between the first nitride semiconductor region and the second nitride semiconductor region. A Si concentration in the intermediate region is not less than 1×1018/cm3 and not more than 1×1019/cm3. A charge density in the intermediate region is 3×1017/cm3 or less.
GaNEX | III-N Technology Newsletter No. 83 | 82
Electronic device including an enhancement-mode hemt and a method of using the same Publication Number: DE102018111319, JP2019197894, US20190348568, CN110474230 Patent Applicant: OSRAM
An optoelectronic semiconductor device and a method for manufacturing an optoelectronic semiconductor device are disclosed. In an embodiment an optoelectronic semiconductor device includes a semiconductor body comprising a first region of a first conductive type, an active region, a second region of a second conductive type and a coupling-out surface, wherein the first region, the active region and the second region are arranged along a stacking direction, wherein the active region extends from a rear surface opposite the coupling-out surface to the coupling-out surface along a longitudinal direction transverse to or perpendicular to the stacking direction, wherein the coupling-out surface is arranged plane-parallel to the rear surface, and wherein the coupling-out surface and the rear surface of the semiconductor body are produced by an etching process.
2405 route des Dolines, CS 10065
06902 Sophia Antipolis, France [email protected] www.knowmade.com