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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