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Mechanisms of Ionization-Induced Carrier Transport and Collection

in Next-Generation III-V Structures

Dale McMorrowRadiation Effects Section

Naval Research LaboratoryWashington, DC

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Outline

• Objectives/Overview

• Motivation

• III-V Technology Overview

• Radiation Effects in III-V Technologies

• NextGen III-V Research Program

• Technology Transfer

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Description of the Effort

• ABCS: Antimonide-Based Compound Semiconductors

• To investigate, using both theory and experiment, the basic mechanisms of ionization-induced carrier deposition, transport, and collection in next-generation antimonide-based III-V compound semiconductor structures and materials

• This is a collaborative effort between the Naval Research Laboratory and Vanderbilt University

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Status of the Effort

• Significant ongoing ABCS technology development• DARPA ABCS Program (2001-2006)• DARPA ISIS Program (2007-present)• Intel CRADA

• Very little is understood about the performance of ABCS technologies in hostile environments

• Experimental and theoretical databases are minimal

• NRL has unique access to Sb-based technology, and has developed the experimental approaches necessary to address their response to ionizing radiation

• Vanderbilt is ideally suited to take the lead on the theory/computational part of this effort

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III-V Semiconductor Material Systems

Ge

Si

GaAs

GaP

InP

AlSb

GaSb

InAs

ZnTe

ZnSeAlP

AlAs

0.45

0.50

0.60

0.80

1.00

1.30

2.00

5.00

0.8

0.4

1.2

1.6

2.0

2.4

2.8

0

5.4 5.6 5.8 6.0 6.2 6.4

Energy Gap (eV) Wavelength (

μ)m

InGaAs

Lattice Constant (Å)

InSb

Lattice Constant, μm

En

erg

y G

ap, e

V

Wa

vele

ng

th, μ

m

GaAs

AlSb

InAs

GaSbInGaAs

AlAs

InP

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III-V Semiconductor Material Systems

Ge

Si

GaAs

GaP

InP

AlSb

GaSb

InAs

AlP

AlAs

0.45

0.50

0.60

0.80

1.00

1.30

2.00

5.00

0.8

0.4

1.2

1.6

2.0

2.4

2.8

05.4 5.6 5.8 6.0 6.2 6.4

Energy Gap (eV)Wavelength (

μ)m

InGaAs

Lattice Constant (Å)

InSb

Higher Speed Sb-based materials have highest electron and hole mobilities and velocities.

Lower Power Consumption Sb-based materials have lowest bandgaps and reach electron peak velocity at lowest electric fields.

GaAs-based HEMTs and HBTsFirst generation:

InP-based HEMTs and HBTsSecond generation:

Sb-based HEMTs and HBTsNext generation:

Ge

Si

GaAs

GaP

InP

AlSb

GaSb

InAs

AlP

AlAs

0.450.50

0.60

0.80

1.001.30

2.00

5.00

0.8

0.4

1.2

1.6

2.0

2.4

2.8

0

0.8

0.4

1.2

1.6

2.0

2.4

2.8

05.4 5.6 5.8 6.0 6.2 6.45.4 5.6 5.8 6.0 6.2 6.4

( )Energy Gap eV (Wavelength

μ)m

InGaAs

Lattice Constant (Å)

InSb

Higher Speed Sb-based materials have highest electron and hole mobilities and velocities.

Lower Power Consumption Sb-based materials have lowest bandgaps and reach electron peak velocity at lowest electric fields.

GaAs-based HEMTs and HBTsFirst generation:GaAs-based HEMTs and HBTsFirst generation:

InP-based HEMTs and HBTsSecond generation:InP-based HEMTs and HBTsSecond generation:

Sb-based HEMTs and HBTsNext generation:Sb-based HEMTs and HBTsNext generation:

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• Low-noise receivers• space-based sensing and communications• portable communications • micro-air-vehicles (MAVs)

Motivations: ABCS Electronics

High-speed, low-power consumption electronics are needed for light-weight power supplies, extension of battery lifetimes, and high data rate transmission

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• High-speed logic circuits• high-speed onboard processing • communications, data transmission• potential for lowest power-delay product• integration with RTDs for enhanced

functionality and low-voltage operation

• InP HEMTs presently hold the record current gain cutoff frequency for any three-terminal device

Motivations: ABCS Electronics

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• Sb-based electronics exhibit:• High electron mobility• High electron velocity• High sheet charge density• Large conduction band offset• <0.5 V operation / low power dissipation• Low noise

• Digital circuits with speeds >100 GHz are anticipated

Motivations: ABCS Electronics

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ABCS Technology Development

• The NRL Microwave Technology Branch is a world leader in the growth, fabrication and characterization of Sb-based HEMTs, p-channel HFETs, and HBTs.

• DARPA ABCS Program (2001-2006): • NRL teamed with Northrop-Grumman Space Technology

(NGST, formerly TRW) to develop next-generation high-speed, low-power HEMT and HBT technology using antimonide heterostructures.

• At the inception of the ABCS program, NRL had been in the forefront of the development of antimonide HEMT technology for more than seven years.

• NRL’s superior material growth and device processing capabilities let to a record high cutoff frequency fT of 250 GHz, and a 90 GHz fT at a record low voltage of 0.1 volts

• NRL growth and processing technology for antimonide HEMTs transferred to NGST via CRADA in FY03.

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ABCS Technology Development

• DARPA ABCS Program Major Milestones:• demonstration of an antimonide HEMT with a record

maximum frequency of oscillation (fmax = 275 GHz) • Demonstration of an order of magnitude less power

consumption than HEMTs based on competitive semiconductor material systems

• The first antimonide-based X-band and W-band MMICs with state-of-the-art low-power performance

Ref: J. Vac. Sci. Technol. B, 17 (3), May 1999

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ABCS Technology Development

• DARPA Integrated Structure is Sensor (ISIS) Program • NRL is again teamed with NGST • Continue to develop next-generation high-speed, low-

power Sb-based HEMT technology. • Intel CRADA

• NRL is also currently teamed with Intel, via a Cooperative Research and Development Agreement (CRADA), to develop advanced p-channel Sb HFETs for use in high-speed complementary logic applications

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• 1.7 μm AlSb buffer layer on GaAs (SI) substrate: accommodates 8% lattice mismatch

• InSb-like interfaces: high electron mobility • Modulation doping in thin InAs(Si) layer: sheet charge densities of 1-4 x 1012/cm2

• Large InAs/InAlAs valence band offset: lower leakage current from holes• InAs sub-channel reduces impact ionization: higher frequency operation

0 50 100 150 200 250 300 350 400 450 500

-1.0

-0.5

0.0

0.5

1.0

AlSb

In0.4Al0.6As

InAs

InAs(Si)

E1E0

E0’

Distance (Å)E

nerg

y (e

V)

ABCS Technology: InAs HEMT

AlSb 125 Å

InAs(Si) 12 ÅAlSb 12 Å

InAs 20 ÅIn0.4Al0.6As 40 Å

SI GaAs substrate

AlSb 1.7 μm

InAs 100 Å

AlSb 30 ÅInAs subchannel 42 Å

AlSb 500 Å

Al 0.7Ga0.3Sb 0.3 μm

6.1 Å Lattice Spacing

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III-V Semiconductor Material Systems

Ge

Si

GaAs

GaP

InP

AlSb

GaSb

InAs

ZnTe

ZnSeAlP

AlAs

0.45

0.50

0.60

0.80

1.00

1.30

2.00

5.00

0.8

0.4

1.2

1.6

2.0

2.4

2.8

0

5.4 5.6 5.8 6.0 6.2 6.4

Energy Gap (eV) Wavelength (

μ)m

InGaAs

Lattice Constant (Å)

InSb

Lattice Constant, μm

En

erg

y G

ap, e

V

Wa

vele

ng

th, μ

m

GaAs

AlSb

InAs

GaSbInGaAs

AlAs

InP

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ABCS Technology: InAsSb HEMT

InAlSb

InAsSb

InAlSb

Type I Band Alignment

InAlSb

InAsSb

InAlSb

Type I Band Alignment

20 Å

150 Å

1.0 μm

1.5 μm

40 Å150 ÅIn0.2Al0.8Sb

InAs0.7Sb0.3

GaAs substrate

In0.4Al 0.6AsInAs

In0.2Al0.8Sb

AlSb

In0.69Al0.31As0.41Sb0.59

75 Å

20 Å

150 Å

1.0 μm

1.5 μm

40 Å150 ÅIn0.2Al0.8Sb

InAs0.7Sb0.3

GaAs substrate

In0.4Al 0.6AsInAs

In0.2Al0.8Sb

AlSb

In0.69Al0.31As0.41Sb0.59

75 Å

6.2 Å Lattice Spacing

• Higher electron mobility and velocity for higher speed.

• Type I band alignment for lower leakage and lower noise figure.

• Reach peak velocity at lower electric field for lower power consumption.

• Complete structure is stable in air for increased stability.

InAsSb HEMT has attractive material properties and unique design flexibility enabling improved high-speed, low-power performance:

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• III-V FETs typically are tolerant to high levels of ionizing radiation• Lack of native oxides• Dominated by displacement damage (DD) effects

• III-V FET-based technologies typically are extremely susceptible to single-event effects

• A primary goal of this program is to develop an understanding of the basic mechanisms of carrier transport and collection that lead to this SEE susceptibility

Radiation Effects in III-V FETs

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• Recent work at NRL demonstrates that 6.1 Å ABCS technology is more tolerant than either GaAs or InP-based technologies

• Due to strong carrier confinement in heterostructure wells

• Weaver, et al., “High tolerance of InAs/AlSb high-electron-mobility transistors”, Appl. Phys. Lett, 87,

173501 (2005).

Rad Effects: TID/DD in III-V FETs

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• GaAs MESFETs and HFETs; Extensive work in 1990s: • Experiment and Simulation (NRL and others)• Charge collection and enhancement mechanisms fairly well

understood

• InP HEMTs: Limited experimental and simulation work• Experimental data similar to that of GaAs devices (NRL)• Simulation results inadequate but reveal significant

differences

• ABCS Devices: • HI and pulsed laser data on 6.1 Å technology (NRL)• No simulation results on 6.1 Å technology• No data/simulation on 6.2 Å or 6.3 Å technologies

Rad Effects: SEE in III-V FETs

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Rad Effects: CC in GaAs HFETs

0 100 200 300 400 500 600 700

-16

-14

-12

-10

-8

-6

-4

-2

0

-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2

0

1

2

3

4

5

6

(a)

VG = -1.0 V

VG = 0.0 V

VG = 0.15 VDrain Signal, mV

Time, ps

(b) 3 MeV α Particle100 fC Deposited Charge

, Collected Charge pC

Gate Bias, V100 fC

Charge Enhancement

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2.0

1.5

1.0

0.5

0.0

(a) t < 0

3E11

1E12Depth,

μm

(b) t < 0

1.2

1.0

0.6

0.6

0.4

0.8

00.10000.20000.30000.40000.50000.60000.70000.80000.90001.0001.1001.2001.3001.4001.5001.6001.7001.8001.9002.0002.1002.2002.3002.4002.5002.6002.7002.8002.9003.0003.1003.2003.3003.4003.500

0.0 0.5 1.0 1.5 2.02.0

1.5

1.0

0.5

0.0

(c) t = 32 ps

DGSDGS

1E14

1E15

3E16

1E16

Position, μm

, Depth

μm

2.0002.5003.0003.5004.0004.5005.0005.5006.0006.5007.0007.5008.0008.5009.0009.50010.0010.5011.0011.5012.0012.5013.0013.5014.0014.5015.0015.5016.0016.5017.0017.5018.0018.5019.0019.5020.00

0.0 0.5 1.0 1.5 2.0

(d) t = 32 ps

1.31.2

1.0

0.7

0.5

Position, μm

Rad Effects: CC in GaAs HFETs

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• 10X - 60X charge enhancement observed• HI and laser excitation

• Associated with S-D current (from power supply)• Barrier lowering at source-substrate barrier• device turned “on”

• Associated with charge deposited below active region• 1 μm to 2 μm most effective

• Current pathway from source, deep through substrate, to drain

Rad Effects: CC in GaAs HFETs

S G DS G D

t<0 ps

50 ps

400 ps

400 ps

t<0 ps

cutline cutline

G G

Electron Density Hole DensityRad Effects: CC in InP HEMTs

• Experiment

• Device simulation• Mechanisms are significantly different from

GaAs

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0.00 0.05 0.10 0.15-15

-10

-5

0

InAlAs InAlAsInGaAs

Depth in Device, mm

t < 0 ps t = 400 ps 1e8 (600 ps)1e18 (600 ps)

Carrier Injection and S-D Current Confined to InGaAs Channel

Rad Effects: CC in InP HEMTs

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0.0 0.2 0.4 0.6 0.8 1.08

10

12

14

16

18

holes

electrons

Position, mm

Excess Hole Density in InAlAs buffer:

appx. 1015 cm-3

Rad Effects: CC in InP HEMTs

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400 ps

Bulk (GaAs MESFET) InP HEMT

Rad Effects: Bulk vs. HEMTs

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Rad Effects: AlSb/InAs HEMTs

0 250 500 750 1000

0.01

0.1

1

-20 0 20 40 60 80 100

0

20

40

τ3 = 440 ns

τ2 = 42 ns

τ3 = 4.8 μsτ2 = 73 ns

GaAs MESFET

InP HEMT

Time, ns

(b)

(a)

InP HEMT

GaAs MESFET

Fig. 4. Comparison of heavy-ion induced drain charge-collection transients measured for a GaAs MESFET and an InGaAs/InAlAs (InP) HEMT for 7.34 MeV·cm2/mg LET(GaAs) ions (5.7 GeV 78Kr at 0° incidence) for a worst-case bias conditions: MESFET: VD = 2.0 V; VG = 0.3 V; HEMT: VD = 1.1 V; VG = -0.4 V. The smooth lines represent least squares fits to biexponential decay functions with the time constants indicated.

-25 0 25 50 75 100 125

0

10

20

30

40

50

InP HEMTV

D = 1.1 V

VG = -0.40 V

InAs HEMTV

D = 0.45 V

VG = -0.50 V

Drain Voltage, mV

Time, ns

Fig. 5 . Comparison of drain charge - collection transients

measured for an InGaAs/InAlAs HEMT and an AlSb/InAs

HEMT for 37 MeV·cm2/mg LET(GaAs) ions (278 MeV 79Br at 45° incidence) for worst-case bias conditions of VD = 1.1 V; VG = -0.4 V and VD = 0.45 V and VG = -0.5 V, respectively.

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Technical Approach

• OBJECTIVE: To investigate, using both theory and experiment, the basic mechanisms of ionization-induced carrier deposition, transport, and collection in next-generation antimonide-based III-V compound semiconductor structures and materials.

• APPROACH: • Experiment: measurement of charge collection

transients in 6.1 Å and 6.2 Å ABCS test structures• Theory: develop a theoretical description to

describe the highly non-equilibrium state induced in heterosructure devices by ionizing radiation; use the experimental data to validate and calibrate the theory

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Technical Approach

• Experimental Approach (NRL): • Test structure selection• Packaging in high-bandwidth packages• High-bandwidth transient measurement• Statistical analysis of ion-induced transients

• Theoretical Approach (VU): • Develop a theoretical description• Evaluate capabilities of various commercial codes and

determine suitability• Use the experimental data to validate and calibrate

the theory • Identify the basic mechanisms of carrier transport and

collection that are responsible for shaping the data

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Technical Approach

• High-bandwidth (12-20 GHz), single-shot transient measurement• Permits direct measurement of ion-induced transients for single

ion strikes for the first time

12-GHzScope

drain bias

source drain

HF package

Heavy-ionIrradiation

50Ω

50Ω

50-GHzBias-T

12-GHzScope

drain bias

source drain

HF package

Heavy-ionIrradiation

50Ω

50Ω

50-GHzBias-T

12-GHzScope

drain bias

source drain

HF package

Heavy-ionIrradiation

50Ω

50Ω

50-GHzBias-T

Fig. 8 . Schematic diagram of the ex perimental set - up used

for measure ment of high - bandwidth transients from

semiconductor structures. The particular configuration

illustrated is for the simultaneous measurement of both

the drain and body electrodes on an SOI te st structure

with the 12 GHz bandwidth single - shot oscilloscope. The

entire temporal profile is measured for both channels for

every ion strike.

-0.5 0.0 0.5 1.0 1.5 2.0-0.5

0.0

0.5

1.0

Drain (45 fC)

Current (mA)

Time (ns)

Drain (75fC)

Body (12 fC)

-0.5

0.0

0.5

1.0

Body (45 fC)

(b)

(a)

Fig. 9. Drain and body charge-collection transients measured in coincidence for two different ion strikes for a 70 nm partially-depleted SOI transistor with body contacts. VD = 1.0 V; all other terminals grounded. 808 MeV 78Kr at 0° incidence.

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Technical Approach

• Theoretical Approach (VU): • One graduate student assigned to this project

(Sandeepan DasGupta)• Vanderbilt will provide access to its Advanced

Computing center for Research and Education (ACCRE), which houses their Beowulf cluster supercomputer

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Progress

• Initial test structures selected• Mounted in high-bandwidth packages• Tested for dc operational characteristics

• Heavy-Ion test scheduled for June

• Vanderbilt student (Sandeepan DasGupta) is getting started• Reading literature• Evaluating available commercial codes• Asking questions

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Key Personnel

• NRL Solid State Electronics Branch• Radiation Effects Branch (McMorrow, Warner)

• NRL Microwave Technology Branch• Brad Boos

• Vanderbilt/ISDE• Robert Reed• Ron Schrimpf• Grad student

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Technology Transfer

• NRL ABCS technology development

program

• ISDE Engineering

• Collaborative R&D, e.g. NRL/Vanderbilt

• DoD vendor relationships

• NASA Goddard

• Through students