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Confidential 1

Prof. Dr. Helge Weman, Founder and CTOCrayoNano, Trondheim, Norway

www.crayonano.com

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AlGaN Nanowire/Graphene Deep UV LEDs

- Changing the UV LED industry

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Introduction

• A University spin-off– CrayoNano originates from several years of

research at the Norwegian University of Science and Technology (NTNU), Trondheim, Norway:

III-V semiconductor nanowires foroptoelectronic device applications

• Large academic funding since 2006– The underlying technology has been funded by

several research projects from the Norwegian Research Council, Nordic Innovation, EU, e.g.

– Over USD 15 million invested so far

• CrayoNano founded in June 2012– IP-portfolio: Semiconductor nanowires on

graphene (9 different patent-families)– Core team of 8 people– HQ in Trondheim, Norway

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CrayoNano Key Personnel

Dr. Helge Weman (CTO and founder)

Dr. Bjørn Ove Fimland(Sr. engineer and founder)

Dr. Dong-Chul Kim(Sr. pr.manager and founder)

Morten Froseth (CEO and co-founder)

• Professor at NTNU• 25 years experience in III-V

structures and devices

• Professor at NTNU• 25 years of experience in MBE

growth of III-V semiconductors

• 10 years experience in semiconductor devices

• 5 years graphene research experience at Samsung

• Serial entrepreneur and start-up investor

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Dheeraj Dasa(MBE/MOCVD growh)

Mazid Munshi(MOVCD growth)

Carl Philip Heimdal(Processing)

Junghwan Huh(Processing)

Cheng Guan Lim(Simulation and modeling)

• MBE/MOCVD growth ofnanowire structures

• Characterization

• MOCVD growth ofnanowire structures

• Characterization

• Wafer and device processing

• Post.doc at NTNUfunded by the Norwegian Research Council.

• 15 years experience within optoelectronic device modeling, simulation and fabrication.

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The Issues of today’s AlGaN UVC LEDs

Very low efficiency• The total external quantum efficiency of

today’s UVC LEDs is only a few percent.

Advanced thermal management needed• In addition to UVC LEDs’ low power

output, their low efficiency creates difficulties at the packaging level.

Use of expensive substrates and materials• UVC LEDs are using expensive AlN

substrates and/or thick AlN buffers.

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• Not yet sufficient to trigger adoption in the main purification and disinfection applications ( ~265 nm), meaning traditional mercury arc lamps are still used for these wavelengths. • According to Minamata convention (2013) mercury based lamps to be phased out in 2020.

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Today’s challenges for AlGaN UVC LEDs

No transparent electrodes• ITO cannot be used (absorbs light < 350 nm).• UVC LED therefore emit light through substrate.- However substrates also absorb in UVC.

Low p-type doping of AlGaN• Due to high p-AlGaN resistance a p-GaN layer is used. - p-GaN absorb light that could have been reflected back.

Low internal quantum efficiency• AlGaN/GaN planar design large issues with lattice mismatch

that affects the crystal quality.

Expensive substrates and materials• In addition traditional MOCVD system cannot be used to the

high temperature growth needed for AlN buffer.- Market prices as high as USD 10 000/Watt !

Low light extraction efficiency• Due to high refractive index difference substrate/air and

absorbing p-GaN light extraction efficiency (LEE) is only ~ 5 %.

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Wall plug efficiency is today only few %!

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External quantum efficiency of today’s AlGaN LEDs

• At 265 nm the external quantum efficiency is ~10 % at the best

• UVC LEDs are also very expensive and have relatively short lifetime

Source: Yole Developpement (2015)

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UVC LED market

• UVC LED is today marginal but expected to be ~ 30% of total UV LED revenue by 2019 (~ $150M).

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CrayoNano’s solution 1

Why nanowires ?

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Lattice mismatch not a big problem

Integration of e.g. III-V on silicon substrate

Lattice mismatch

Can do growth of hetero structures in both and radial direction (core-shell).

Several potential device applications LEDs (e.g. Glo, Aledia, Osram, LG, Samsung) Solar cells (e.g. Sol Voltaics, Gasp Solar) Transistors (e.g. IBM etc) Sensors Lasers ….

Due to small size and quantum effects potential to be much more efficient/sensitive

Axial Radial

III-V NW

Problem No problem

III-V thin film

Radial p-n junction nanowire

array solar cell

Si substrate

Why semiconductor nanowires (NWs)?

Si substrate

Grown bottom-up Using catalyst or catalyst-free epi-growth(MBE or MOCVD)

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Companies working on InGaN nanowire visible LEDs(selective area growth using MOCVD)

• Faster growth rates than thin film• Much lower material consumption than thin film• Light emission area = up to 5X the 2D area = more light/mm2, less efficiency droop• Multiple colors on chip possible (RGB displays)• Due to periodic geometry beam properties can be designed (photonic crystal effect)

Overview of structure of visible LEDs based on nanowires

Source: Glo and Aledia

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AlGaN and AlN nanowire UVC LEDs on Si substrate(Prof. Mi, McGill University)

Z. Mi’s group at McGill University, Canada. Scientific Reports, Feb. 16, 2015.

• 80% IQE and good electrical characteristics.

• p-type AlN doping ~ 10x16/cm3- However very low light extraction, due to non-transparent substrate (Si) and top-contact.

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CrayoNano’s solution 2

Why graphene ?

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Graphene – The New “Wonder Material”A one-atomic layer of carbon atoms in a honeycomb crystal lattice

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Outstanding properties of Graphene:• Record electrical & thermal conductivity• Flexible• Transparent to light (all wavelengths)• Thinnest and strongest material ever

If it would be possible to use graphene as an epitaxial substrate to grow semiconductors this could enable radical new device applications….

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CrayoNano’s TechnologyFirst results achieved at NTNU in 2010:

SEM image of self-catalysedGaAs NWs on graphene

High-quality vertical GaAs NWs grown epitaxially on graphene

Munshi et al., Nano Letters, 12, 4570-4576 (2012)

Cross section HRTEM image GaAs NW/graphene interface

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3.0 3.5 5.0 5.5 6.0 6.5 7.00.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

dcb

acub

ba

ahex

ZnO

InSb

AlP

InAs

Bandga

p, E

g (

eV

)

Lattice constant, a (Å)

InN

GaP

GaAs

Si

InP

AlAs

AlSb

GaSb

GaN

6.3%

8.2%

H- and B-sites H- and B-sites

H- or B-sites H- and B-sites

b

c d

HB

H

B

H

B

H H

a

Near lattice match for some semiconductors (AlN, GaN, ZnO, InAs) Nanowire growth on graphene could be possible for any semiconductor

A new platform to build next generation semiconductor devices

Munshi et al., Nano Letters 12, 4570 (2012)Munshi and Weman, Phys. Status Solidi RRL 7, 713 (2013)

Generic model for epitaxial growth of semiconductors on graphene

Semiconductor atoms in (111) planes on graphene

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CrayoNano’s solutionCombined graphene substrate-electrodeAlGaN nanowires on graphene, where graphene used as a substrate and transparent electrode.+ Graphene is transparent to all wavelengths with low sheet resistance (T~ 95% even in UVC).

+ Enables vertical injection (no current crowding).+ Can be scaled up to large wafer sizes.

Nanowire array based design• Small lattice mismatch with graphene < 2%+ AlGaN nanowires are dislocation free (high IQE).• Efficient p-AlGaN doping in nanowires.+ Absorbing p-GaN can be avoided.• Waveguide and photonic crystal effects.+ Very high light extraction efficiency.• No special high-temp AlN buffer growth needed.+ Standard MOCVD systems can be used.

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AlGaN nanowire/graphene flip-chip design

GaN lattice mismatch ~2.1%

Wall plug efficiency (WPE) similar to near-UV LEDs is

expected (> 40%)!

graphene

AlGaNnanowires

P-electrode (and reflector)

UVC light emission

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CVD graphene production systems

Industrial production

• Large scale graphene production is now being established by both larger and smaller producers based on low cost roll-to-roll and wafer processes (including transfer onto any target support).

Rapid cost reduction

• The price of graphene is rapidly declining due to the current oversupply market situation.

R2R pilot production of CVD graphene by Hanwha Techwin, Korea.(CrayoNano and Hanwha Techwin signed MoU in 2015)

8’’ CVD graphene systems developed by Aixtron, Germany

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LED Value Chain and Business Model

• CrayoNano targets to develop and commercialize deep UV LED dies.• Initial production will be based on own small scale production that will be further scaled up

through existing foundries.• Processed dies will be sold to existing LED packaging companies for further use in different

applications, e.g. disinfection, sterilization, sensing and curing.• CrayoNano is discussing with leading LED companies for joint collaboration and investment.

Substrate UV Die / Chip UV LED PackageUV LED Array /

ModuleUV LED System

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CrayoNano’s Technology Status

GaN/AlGaN nanowireson graphene

• Through our academic partners (Norway, Germany, Japan and China) we have recently successfully demonstrated growth of random & positioned AlGaN nanowires and nano-pyramids on graphene.

• Present work is focused on making UV LED prototypes.

Random AlGaN nanowires Random AlGaN nanopyramids

Densely positioned AlGaN nanopyramids

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• Very high nucleation yield after optimizing nucleation layer.

• Growth of axial c-plane AlGaNquantum wells (QWs) in active layer.

• CL spectrum showing emission at 265 nm (and 525 nm).

• UVC LED prototypes now being developed…

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265 nm

Self-assembled growth of vertical AlGaN nanowires on graphene

CL spectrum of AlGaN NWs grown on graphene

525 nm

Selective area growth of random AlGAN nanowiresin 10 mm hole mask on graphene.

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Development of patterned hole array maskon graphene for selective area growth of AlGaN nano wires/pyramids

Hole array (pitch = 1 μm) oxide mask (Al2O3/SiO2) on CVD graphene wafer.

Hole diameter from 80 to 200 nm by control of the EBL parameters.

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Dense AlGaN/GaN nanopyramid array on graphene

Very high nucleation yield after optimizing nucleation layer

AlGaN nanopyramids with active quantum well layer on semi-polar side facets

Nano-pyramid array UVC LED device prototypes now being developed….

Hole maskGrapheneSilica glass

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Contact Information:

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Prof. Dr. Helge Weman, CTOCrayoNano AS7052 Trondheim, NorwayMob. +47-918 97658,helge.weman@crayonano.comhttp://www.crayonano.com