Local Electronic and Chemical Structure at GaN, AlGaN and SiC Heterointerfaces

• Wide Band Gap Semiconductors

• Low Energy Electron-Excited Nanoscale Luminescence (LEEN) Spectroscopy

• Metal/AlGaN Schottky Barriers: Nanoscale Alloy Changes

• GaN/Al2O3 Heterojunctions: Interdiffusion, Impurity Complexes, and Localized States

• Metal/4H-SiC Schottky Barriers: Interface States vs. Defects

• Interface Chemical and Electronic Trends

YoramFest 10.10.04 Tel Aviv, Israel

Once upon a time in Tel Aviv and Rochester . . . .

GaN and SiC Collaborators

At Ohio State:Shawn Bradley UHV SEM, SIMS Dr. Xiaoling Sun UHV SEM CLS, AESDr. Stephen Goss UHV SEM CLS, SIMS Sergey Tumakha UHV SEM CLS

At Cornell University:Dr. Bill Schaff MOCVD, MBE Prof. Les EastmanMOCVD, MBE

Michael Murphy MOCVD, MBE, µ, ρ

At Wright State University:Dr. David C. Look EC Dopant Profiles

At Lincoln Laboratories:Dr. Richard Molnar GaN HVPE

NASA:Dr. Robert Okojie 4H-SiC Interfaces

This Work Supported by NSF, DOE, ONR, AFOSR, and NASA

GaN Applications• UV/Blue/ white LED (traffic signals, automotive, full

color displays, interior lighting, …)• Blue/violet LDs. (4-8 GB CD-ROM storage, high

resolution printers…)• UV solar blind Detectors (sterilization sensor, missile

tracking/guiding sensor …) • Microwave High power HEMTs (radar, cell

phones…)• Low noise, radiation hard transistors (high

temperature sensors, space-flight instrumentation…)

Nanoscale Electronic Structures

Need To Probe Local Band Structure and Defects

Schottky Barrier Quantum Well

2 DEG Junction Insulator-SC Template

Nanoscale Electronic Structures

Need To Probe Local Band Structure and Defects

Schottky Barrier Quantum Well

2 DEG Junction Insulator-SC Template

Low Energy Electron-Excited Nanometer Scale Luminescence Spectroscopy

EBeam = 0.1 - 4.0 keVI ≈ 1 µA, Spot Size ≈ 500 µm

hv1hv2

hv3

e-

Energy-Dependent Depth of Excitation Enables Probe of Localized States, Heterojunction Band Gaps, New Compounds, and Ultra-Thin Layers on a nm Scale

x

hν1

hν3

hν2

EC

EV

ET

0 1 2 3 4 5 6-20

0

20

40

60

80

100

120

140

160

180

200

220

C = 2.39a = 1.29

RB = C ξa

Depth of MaximumEnergy Loss (U0)

Everhart-Hoff dE/dx vs depth

Bohr-BetheRange (RB)

RB o

r U

0 (nm

)

Incident Electron Energy (keV)0 20 40 60 80 100 120

-10

0

10

20

30

40

50

60

70

80

90

100

4.0 kV2.0 kV

1.0 kV

0.5 kV

Depth (nm)

Ene

rgy

Los

s (eV

/nm

)

GaN Depth Dependence of Electron-Excited NanoscaleLuminescence Spectroscopy

After Everhart and Hoff, J. Appl. Phys. 42, 5837 (1971)

Depth-Resolved CLS: Si-SiO2

0 20 40 60 80 100 1200

10

20

30

40

50

60

70

80

90

100

Interface

0 10 20 30Maximum Energy Loss U0(nm)

Beam Energy (keV)

2.0 eV Interface Defect2.7 eV E2' SiO2 Defect4.3 eV Si Feature

Inte

nsity

(Rel

. Uni

ts)

Total Range RB (nm)

0.5 1.0 1.5 2.0 2.5 3.0

5 nm SiO2

1 ML SiO2 (RPAO) Si

1 ML N (RPAN)

Transition Region:RB ≈ 18 nm, U0 ≈ 6 nm

2.7 eV SiO2 Emission:RB ≈ 10 nm, U0 ≈ 3 nm

UHV CLS Using Auger Microprobe

•Quantum-Scale (5 nm)Analysis of Electronic States and Morphology

•UHV Control of Surface and Interface

•0.5 nm Resolution for UV/IR CL Spectra10K-300K,

• 50 meV Resolution Auger Electron Spectroscopy

Monochromator

PMT

•8×10-11 Torr•0.5 - 25 keV Electron Probe Energy

JEOL 7800F

Schottky Contacts to III-N materials• Schottky contacts to AlGaN and AlGaN/GaN devices: Crucial

for device operation– High barrier for leakage current reduction/ better gate control

• Carrier transport through AlGaN/GaN Schottky contacts is not well explained

• Experimental Approach: – UHV Metal Deposition on Representative, Chemically-Cleaned Surfaces

– Internal Photoemission Spectroscopy (IPE)

– Nanoscale Depth-Resolved Cathodoluminescence Spectroscopy (LEEN)

– Secondary Ion Mass Spectrometry (SIMS)

Use IPE, CLS, and SIMS to Correlate Changes in Schottky Barrier Height with Chemistry/Processing

UHV Ohmic and Schottky Deposition• 1×10-10 Torr Base Pressure• Thermal and E-beam Sources• Ti/Al/Ti/Au Ohmic Contacts

– 850 °C UHV Anneal, 30 seconds

• 1 mm and 0.5 mm Ni Schottky Contacts

• Different Surface Treatments Applied before Ni Deposition

Organic + HCl + Buffered HF+ UV/O3 Cleaning (Hg lamp + O2)+ UV/O3 Cleaning + Buffered HF

Al0.35Ga0.65N (25 nm)

AlN (7 nm)GaN (1 µm)

Al2O3

Ohmic

Schottky

Little YL140 meV8050.331235 (Wafer 1)

730

Mobility(300 K)

0.35

Al mole fraction

Higher YL330 meV1041 (Wafer 2)

AlGaN FWHMUHV Annealing Performed after

Diode Deposition

Internal Photoemission Spectroscopy (IPE)

1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

φb2[Pho

tocu

rren

t/Pho

ton]

1/2 (a

rb. u

nits

)Photon Energy (eV)

Oscillations from thin-film interference

φb1

2)( BqhY φν −∝

X-intercept of Y1/2 plot gives Schottky barrier heightFowler, Phys. Rev. 38, 45 (1931)

hν

hνqφb

•IPE: Yields True Barrier Height(s)

•I-V, C-V: SBH(s) Weighted Averages

(Parallel Schottky Contacts to Si Observed with IPE (Okumura, et al. J. Appl. Phys. 54, 922 (1983))

More than One SBH Measurable

1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.30.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

(Pho

tocu

rrent

/Pho

ton)

1/2 A

rb. U

nits

Photon Energy (eV)

D1HCl1235

Wafer 1 IPE Schottky Barriers

1.35

1.40

1.45

1.50

1.55

1.60

1.65

1.70

D1 D2 D3 D4 D5 D6 D7 D9 D10

solvent+HFUV/O3 only

+325 C, 10 min+425 C, 10 min

UV/O3 + HF

SB

H (e

V)

1 2 3 4 5 6 7

1.40

1.45

1.50

1.55

1.60

1.65

1.70

SBH first slopeSBH second slope

SB

H a

fter 3

25 o C

ann

eal (

eV)

diode

HF+HCl

UV/O3

•Two Thresholds Common to Solvent/HF and UV/O3 Diodes with 325 °C Anneal

•UV/O3 Diodes Yield Larger SBH’s

→ Surface Oxidation Enhances Observed SBH (essentially MOS)

•Two Thresholds → Multiple SBH’s

- Not observed until 325 °C Anneal

•Marked SBH increase with 325 °C Anneal

- More intimate metal- AlGaN contact Ni diffusing through contamination layer(Ishikawa, et al. J. Appl. Phys. 81, 1315 (1997))

- Observed with C-V for Ni/AlGaN (Arulkumaran, et al. IEEE Trans. Elec. Dev. 48, 573 (2001))

S.T. Bradley et al., Appl. Phys. Lett. 85, 1368 (2004)

1.40

1.45

1.50

1.55

1.60

1.65

1.70

1.75

1.80

SB

H (e

V)

+ 500 C 20 min

+ 425 C 20 min

D1 D2 D3 D4 D5 D6 D7 D8 D10 D11

no anneal + 325 C 20 min

HF+HCl

UV/O3+HF strip

1 2 3 4 5 6 7 8 9 10 11

1.35

1.40

1.45

1.50

1.55

1.60

1.65

1.70

1.75

1.80

SBH

(eV)

Diode

HF+HClUV/O3+HF strip

Wafer 2 IPE Schottky Barriers

• UV/O3 + HF treatment Yields Lower SBH After All Anneals

φb2

φb1

•Similar Marked Increase in SBH with 325 °C Anneal for HCl+HF Etch

•I-V Reverse Current Consistent with Increase in SBH with Anneal S.T. Bradley et al., Appl. Phys. Lett. 85, 1368 (2004)

3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.210

100

1000

10000

Lum

ines

cenc

e In

tens

ity (A

rb. U

nits

)

Photon Energy

1 2 3 4 5 6 7 8 10 11

3.913.71

3.60

3.63 1 keV excitation12 K

Shift in AlGaN Emission Correlates with Changes in SBH → Local Al Alloy Variation

HF+HClUV/O3+HF

Wafer 2 Low Temperature Interface LEEN Spectra: Through the Metal

• Two AlGaN NBE Emissions• Lower AlGaN NBE Peak

Increases with UV/O3 + HF cleaning

• AES vs. Process Shows: -UV/O3 Process Oxidizes Surface-Subsequent HF Treatment Removes O

• SIMS Reveals: > 30% Lower AlN-/GaN- Ion Yield and Less Abrupt Ni/AlGaN Interface for UV/O3 -Treated Diodes

• Low Temperature LEEN Reveals Broadening of Peaks→ Compositional Disorder

PHI TRIFT III Time-of-Flight SIMS

• ~ ppb Sensitivity for Some Elements, 1-2 milli-amu Mass Resolution

• Depth Profiling and Imaging Capability

Ga+

Cs+

Pre-SpectrometerBlanker

SED

Detector

ContrastDiaphragm

ESA 1

ESA 2ESA 3

EnergySlit

Post-SpectrometerBlanker

Sam

ple

Ni/AlGaN Interface Chemistry

• Top 20% of AlGaNOxidized as AlO and GaO

0 20 40 60 80 100 120

1

10

100

1000

GS 1235 Wet etch and UV ozone processingSmoothed

Inte

nsity

X Axis Title

Ni GaN AlN AlO GaO

0 20 40 60 80 100

1

10

100

1000

GS 1235 Wet etch and UV ozone processingSmoothed

Inte

nsity

Sputter Time

Ni GaN AlN NiN NiO

• Top 20% of AlGaNContains NiN and NiOReaction Products

Ni/AlGaN Interface Chemical Changes with Processing

GaN

HCL+HF HCL+HF, 325oC Anneal

HCL+HF+UV/O3 + HF, 500oC AnnealHCL+HF+UV/O3, 325oC Anneal

GaN GaN

GaN

Ni

Ni

Ni

Ni

~ nm O, C layer

multi-nm GaO, AlO

φb1 Φb1 + Φb2

~ nm O, C layer

Ni penetrates adventitious layer

Φb1 + Φ’’b2Φb1 + Φ’b2

Thicker (AlO>GaO) oxide layer forms; Al/Ga composition in AlGaNchanges.

AlO>GaO) layer largely removed; Ni contacts both Al-deficient AlGaNlayer and AlGaN layer

Al0.3Ga0.7N Al0.3Ga0.7N

Al<0.3Ga>0.7NAl<0.3Ga>0.7N

Ni/AlGaN Schottky Barrier Summary

• Chemical and Thermal Treatments Alter SBH’s over Range of 100’s of meV

• IPE Detects Double Barriers (200 meV separation)

• LEEN Detects Dual Al Content AlGaN

• SIMS Reveals > 30% Al Content Changes Consistent with CLS and IPE

- Interfacial Carbon Also Affects SBH’s; Cl, F Much Less So

→ Al Content Changes Dominate SBH Variation

Highly n-Type Layer Near HVPE GaN-Sapphire InterfaceW. Götz et al., Mat. Res. Soc. Symp. Proc. 44, 525 (1997) D.C. Look and R.J. Molnar, Appl. Phys. Lett. 70, 3377 (1997)

O Diffuses into GaNG. Popovici et al., Appl. Phys. Lett. 71, 3385 (1997)X.L. Xu et al. Appl. Phys. Lett. 76, 152 (2000)

X-Sectional Micro-CLS Reveals NewDonor Bound Exciton at Degenerate Interface - Extends 1-2 µm

New Donor Emission Correlates Spatially with SIMS

GaN/Al2O3 Interfaces: Background

Al2O3

GaN

S. H. Goss, X. L. Sun, et al. Appl. Phys. Lett. 78, 3630 (2001)

340 360 380 400 420 4400.0

5.0k

10.0k

15.0k

20.0k

25.0k

30.0k

x 3

dint

3.083eV

3.149eV3.176eV

3.447eV3.473eV

8µm

10.5µm

5.5µm

4µm

3µm

1µm

0.5µm

0.25µm

10K, 5keV, 1nA

Energy (eV)

CL

Inte

nsity

(a.u

.)

Wavelength (nm)

3.6 3.4 3.2 3 2.8

3.243eV3.268eV

0 2 4 6 8 10 12

1E17

1E18

1E19

1E20

Subs

trate S

urfa

ce

Inte

rface

bulk GaN

O c

once

ntra

tion(

atom

s/cc

)

Distance from interface (µm)

O concentration

0.0

0.2

0.4

0.6

0.8

1.0

1.2C

L in

t rat

ios

of D

X' /D

0 X CL intensity ratios

Low-T CL GaN/Al2O3 Depth Profile: New Interface Donors & Reaction Products

300 350 400 450 500

D0X

3.56 eV

CL

Inte

nsity

(a.u

.)

Wavelength (nm)

dint(µm)

15

12

10

7.5

1

0.25

-0.25

CL,10K, 5 keV, 1 nA

5

Energy (eV)4 3.83.6 3.4 3.2 3 2.8 2.6

3.88eV

3.30eV3.40eV

• 34 meV O Donor• Band Tailing & Filling at

Highest Doping

340 360 380 400 420

0

2000

4000

6000

8000

10000

508x1014

nint(cm-2)

98x1014

18x1014

8x1014

#209, 17µm0.4µm from interface

#196, 11µm 0.5 umfrom interface

#1106,5µm, 0.3µm from interface

#1089,0.5µm, 0.5µm from interface

Energy (eV)

CL

Inte

nsity

(a.u

.)

Wavelength(nm)

3.6 3.4 3.2 3

10K, 5 KeV, 1 nA

Above-GaN Energy Shoulder:AlGaN Formation

S.H. Goss, et al., Appl. Phys. Lett.78, 3630 (2001).

X. Sun et al., J. Vac. Sci. Technol., in press.

Auger Images of Sample TH1011-1,3 (E=10 keV, I=3.3 nA)High

Low

C Ga

N OAl

GaN

Sapphire

SEM

Cross-Sectional SIMS Images at GaN-Al2O3 Interfaces

GaN

Al2O3

• Filamentary GaO Image → O Grain Boundary Diffusion• GaO, GaON, AlGaO & AlGaON Fragments → Ga-O Bonding•AlN, AlGaN Fragments → AlGaN Alloy Formation

GaN/Al2O3 Interface Summary• New Shallow Donor Transition Tracks with Interface

SIMS [O] Concentrations → High nint Due to O Diffusion from Al2O3 Into GaN

• Interface Defects Can Extend Microns Into GaN and Al2O3

• Al-N-O Complex Formation→ N Indiffusion and Defect Emission

• Evidence for GaN-Al Alloying: Al Indiffusion, High Energy Emission

SiC Schottky Barrier Formation: Background

• Localized States Influence Charge Transfer & Barrier Height

• Until Now: Moderate Interface State Density Only Inferred from Band Bending vs. ΦM since:

Conventional Techniques (e.g., C-V, DLTS) Can’t Probe nm-Scale Interface Region

• Now: Near-Interface States Measured Directly By NanoscaleDepth-Resolved CL

After A. Itoh, H. Matsunami, Phys Stat. Sol. 162, 389 (1997)

ΦB=0.7*ΦM-1.95

Ideal ΦB=ΦM -χ

χEvac

Au – Induced 4H-SiC Interface States (0.5 keV)

• Au Deposition Introduces 1.7 – 2.0 eV Deep Level Emission

• Emission Highly Localized to Interface Region

1.5 2.0 2.5 3.0 3.5

10

100

1000

Energy (eV)

Log

CL

Inte

nsity

(a.u

.) 4 nm Au on SiC (Si face)

Bare SiC

Au/SiC - Bare SiC Difference

1.7 - 2 eV

EB = 0.5 keV (U0 = 2-4 nm)

1.5 2.0 2.5 3.0 3.5

10

100

1000

Energy (eV)

Log

CL

Inte

nsity

(a.u

.) 4 nm Au on SiC (Si face)

Bare SiC

Au/SiC - Bare SiC Difference

1.7 - 2 eV

EB = 0.5 keV (U0 = 2-4 nm)

1.5 2.0 2.5 3.0 3.5

10

100

1000

Energy (eV)

Log

CL

Inte

nsity

(a.u

.) 4 nm Au on SiC (Si face)

Bare SiC

Au/SiC - Bare SiC Difference

1.7 - 2 eV

EB = 0.5 keV (U0 = 2-4 nm)

S. Tumakha et al., J. Vac. Sci. Technol., in press.

1.5 2.0 2.5 3.0 3.5

10

100

1000

Pre-Anneal Au region 800 Co 1hr. Au region

Au-Deposited AreaEB = 0.5 keV (U0 = 2-4 nm)

Energy (eV)

Log

CL

Inte

nsity

(a.u

.)

1.5 2.0 2.5 3.0 3.5

10

100

1000

Pre-anneal, bare SiC region 800 Co 1 hr. bare SiC region

Adjacent Bare SiC AreaEB = 0.5 keV (U0 = 2-4 nm)

Energy (eV)

Log

CL

Inte

nsity

(a.u

.)

Au-Deposited vs. Bare 4H-SiC Comparison Only Au-Covered Area Changes with Annealing

1.5 2.0 2.5 3.0 3.50

1000

2000

EB = 500 eV (U0 = 2-4 nm)

Pre-Anneal Post-500 oC Anneal Post-700 oC Anneal

Energy (eV)

Log

CL

Inte

nsity

(a.u

.)

Unreactive Metals: Au, Ag/ 4H-SiC Interface States

• 4 nm Au, ~ 3nm Ag Induce 1.7-2.0 eV Emissions • 800 - 900°C Anneals Decrease 1.7-2.0 eV Emissions→ Au and Ag Exhibit Analogous Behavior with Deposition

and Annealing

~ 3 nm Ag/4H-SiC

1.5 2.0 2.5 3.0 3.5

100

1000

10000

Pre-Anneal - Post-AnnealDifference

Post-Anneal

Au region pre-anneal 800oC Au region 900oC Au region Difference: Au feature

removed by annealing

4 nm Au on SiC(Si face)EB = 1 keV (U0 = 4-5 nm)

Energy (eV)

Log

CL

Inte

nsity

(a.u

.)

Pre-Anneal

UHV Thermally-Activated Deep Level Emission

• Highly N-doped (> 2 x 1019 cm-3)4H-SiC(0001) Annealed in UHV

• New Emissions Appear at 2.47 eVand ~ 1.9 eV

• Similar Activation Energy as Oxidized 4H-SiC(0001)

• 1.9 eV Transition Appears After Emergence of 2.47 eV Peak

→ Both Related to Stacking Faults 1.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50

Unannealed

2.35 eV

n > 2.0 x 1019

1.9 eV 2.47 eV

2.47 eV

3.22 eV

3.14 eV

3.22 eV3.16 eV

1hr 1100oC

1150oC 2hr

1150oC 2hr

1hr 900oC

Wavelength (nm)

CL

Inte

nsity

(a.u

.)

Energy (eV)

1 hr 800oC

1hr 1000oC

1150oC 0.5hr

800 700 600 500 400

x4

U0=35 nmEB=3 keV

x4

Brillson L.J., Tumakha S. et al. J. Phys.: Condens. Matter 16 (2004) S1733–S1754

Electroluminescence of Electrically-Stressed 4H-SiC

• 2.65-2.9 eV Associated with Triangular Stacking Faults [Single Stacking Faults Produced under Electrical Stress]

• 1.7-1.9 eV Emission From Partial Dislocations Bounding Stacking Fault Planes

• 2.45 eV and 1.9 eV Similar to Double Stacking Faults Produced Under Thermal Stress L.J. Brillson, S. Tumakha, et al., Appl. Phys. Lett. 81, 2785 (2002)

A.Galeckas, J. Linnros, and P. Pirouz, Appl. Phys. Lett. 81, 883 (2002)

Reactive Metals: Ti, Ni/4H-SiC Interface States• ~ 3 nm Ti or Ni Deposition Induce No Major Changes

• 800-900 °C Anneals Introduce New 2.85 eV Emission → Ti and Ni Interfaces Are Qualitatively Different

from Au and Ag Interfaces

1.5 2.0 2.5 3.0 3.5

200

400

600

800

1000

1200

1400

1600

1800

2000 EB = 1 keV, U0 = 4-5 nm)

Before Anneal Post 800 oC Anneal Difference Curve

CL In

tens

ity (a

.u.)

Energy (eV)

2.85 eV

1.5 2.0 2.5 3.0 3.5

200

400

600

800

1000 1.5 2.0 2.5 3.0 3.5

200

400

600

800

1000 1.5 2.0 2.5 3.0 3.5

200

400

600

800

1000 1.5 2.0 2.5 3.0 3.5

200

400

600

800

1000

CL

Inte

nsity

(a.u

.) C

L In

tens

ity (a

.u.)

CL

Inte

nsity

(a.u

.)

SiC Ni

Energy (eV)

500 oC

SiC Ni

700 oC

SiC Ni

900 oC

EB = 500 eV (U0 = 2-4 nm)

SiC Ni

1100 oC

4H-SiC Schematic Energy Level Transitions

EC

EV

EG= 3.2 eV

2.7-2.9 eV

Dislocation-Related (VSi )

2.5 eV

3C Stacking Faults (2SF)

~2.4 eV

3C Inclusions

1.7-1.9 eV

Au, Ag-Induced States

ΦB

Ti, Ni-Induced States

n-ΦB (Si) Range

1.1-1.8 eV

Multiple Deep Defect Levels with Energies Near ΦB Fermi Levels→ Role of Morphological Defects or Mobile Point Defects

3C Stacking Faults (1SF)

1.7-1.9 eV2.7-2.9 eV

~ 2.3 eV

Metal/4H-SiC Schottky Barrier Summary

• No Metal-Specific Interface States Observed

• Metal-Induced States Similar to States Associated with Dislocations or Stacking Faults

• Major Effect with Non-Reactive Metals –Consistent with Diffusion Processes

• Minor Effect with High Reactivity Metals –Consistent with Limited or Si/C Balanced Reactions

• Mobile Native Defects vs. Extrinsic Metal-Induced States Are Dominant SiC-Metal Interface States

Overall Summary• Depth-Resolved Optical Emission from Localized Electronic

States and Band Structure on Nanometer Scale

→ Multiple Deep Levels / New Phases at Wide Gap Semiconductor Surfaces and Interfaces

• Three Types of Wide Gap Interface Electronic Phenomena:

1. Ni/AlGaN: Ternary Alloy Changes That Correlate with Schottky Barriers

2. GaN/Al2O3: Interdiffusion That Produces Impurity Complexes, Localized States & Degenerate Carrier Concentrations

3. 4H-SiC(100)/Metal Interfaces: Defect Movements That Depend on Metal Diffusion vs. Reaction

→ Key Role of Chemical Interactions at the Nanoscale Interfaces

Happy Birthday, Yoram!

Possible Mechanisms for Au-Induced Electronic States• Interdiffusion: Increase in 1.7-1.9 eV Emission After Au

Deposition and Before Annealing → Au Film May Induce Si-Au Mixing → New Native Defects (e.g., VSi and AuI)

Vacancy complex

Au Au

SF complex

Au

Interstitial

After annealing (more diffusion)

AuEc

Ev

Before annealing

Au level

Si

0 5 10 15 20 25 30

1

10

100

1000

10000

~ 10-15 nm

Total Ion Au C Si

Sputter time (s)

Ion

coun

t

• Defect Complex Formation:Decrease in 1.7-2.0 eV Emission After Annealing → Au May Complex with Native Defects → Passivate

SIMS Shows Au Diffuses ~ 10 nm Into SiAfter 800°C /900°C Annealing

VSi

Low Temperature LEEN/CL Maps: Wafer 1

• Maps Reveal Regions of AlGaN Near Band Edge Nonuniformity

5µm

Low Al% AlGaN NBE (3.85 eV) High Al% AlGaN NBE (3.94 eV)

• Complementary Maps Correlate with Multiple AlGaN Near Band Edge Emissions