wide-bandgap semiconductors in space: appreciating the
TRANSCRIPT
National Aeronautics and Space Administration
Wide-Bandgap Semiconductors in Space: Appreciating the Benefits but Understanding the Risks
Jean-Marie LauensteinNASA GSFC, Greenbelt, MD, USA
1To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
Acronyms and Abbreviations
2To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
Acronym Definition
2-D Two Dimensional
AlGaN/AlN Aluminum Gallium Nitride/Aluminum Nitride
BVDSS Drain-Source Breakdown Voltage
C Carbon
DDD Displacement Damage Dose
EC Conduction Band Energy
EF Fermi Level Energy
Egap Bandgap Energy
ESA European Space Agency
EV Valance Band Energy
FIT Failures In Time
FOM Figure of Merit
FY Fiscal Year
GaAs Gallium Arsenide
GaN Gallium Nitride
Ga2O3 Gallium Oxide
GCR Galactic Cosmic Ray
GEO Geostationary Earth Orbit
HEMT High Electron Mobility Transistor
Acronym Definition
ID Drain Current
IDSS Drain-Source Leakage Current
IG Gate Current
IGSS Gate-Source Leakage Current
InP Indium Phosphide
IR Reverse Current
ISS International Space Station
JBS Junction Barrier Schottky diode
JFET Junction Field Effect Transistor
LEO Low Earth Orbit
LET Linear Energy Transfer
MESFET Metal-Semiconductor Field Effect Transistor
MOSFET Metal Oxide Semiconductor Field Effect Transistor
NO Nitric Oxide
PIGS Post-Irradiation Gate Stress
R&D Research and Development
RDS_ON On-State Drain-Source Resistance
RF Radio Frequency
RHA Radiation Hardness Assurance
RHBP Radiation Hardened By Process
Acronym Definition
SBD Schottky Barrier Diode
SBIR Small Business Innovative Research
SEB/GR Single-Event Burnout/Gate Rupture
SEE Single-Event Effect
Si Silicon
SiC Silicon Carbide
Sn Tin
SOA State Of the Art; Safe Operating Area
STMD Space Technology Mission Directorate
SWAP Size, Weight, And Power
TAMU Texas A&M University cyclotron facility
TID Total Ionizing Dose
UWBG Ultra-Wide Bandgap
VDMOS Vertical Double-diffused MOSFET
VDS Drain-Source Voltage
VGS Gate-Source Voltage
VR Reverse-bias Voltage
VTH Gate Threshold Voltage
WBG Wide Bandgap
Xe Xenon
•
Outline
3To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
Overview
WBG
RH
AThe Future
Reprinted with permission from Yao, et al., JVSTB, vol. 35, p. 03D113. Copyright 2017, American Vacuum Society
Sn-doped Ga2O3 wafer
• Overview– Bandgaps: the simple explanation– Wide-bandgap (WBG) technology advantages & applications– Space environment hazards
• Radiation Hardness Assurance (RHA) of Commercially-Mature WBG Semiconductors – SiC discrete power devices– GaN high electron mobility transistors (HEMTs):
• RF• Enhancement-mode
• A Glimpse into the WBG Semiconductor Horizon– Qualification standardization & technology maturation– The future of SiC and GaN– Ultra-Wide Bandgap (UWBG) semiconductors
• Diamond• Ga2O3
0 < ct)
< ro ~
•
( ac) ) I
Wide-Bandgap Technology Overview:What’s a Bandgap? (Simply Speaking)
4To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
Conduction Band
ValenceBandE
nerg
y (E
) [eV
]
Egap
• As atoms come together to form a crystal, their electron shells form bands: – the highest-energy band containing electrons at 0 K = Valence Band– the next highest energy band = Conduction Band
• Electrons in the conduction band (and subsequent holes in the valence band) are able to move freely about the lattice and thus conduct current
• In order to become conducting, an electron must have enough energy to jump the gap– this jump can be assisted by traps, or energy states, located in the band gap
Wide bandgap materials have different electrical properties than conventional bandgap materials (e.g., Si) due to their different band structure and band gap
Overview
0 < CD
< ro :E •
Wide-Bandgap Technology Overview:Properties Associated with the Bandgap
5To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
• WBG semiconductors can:– Operate at higher temperatures without “going intrinsic”– Block higher voltages for a given thickness of material (breakdown voltage ∝ (Egap)4)– Switch at higher speeds due in part to higher saturation velocities– … and other WBG-material specific advantages
Overview
• 0 7 < ct)
< 6 ro ~
~ Conventional 6 [::=J WBG -
~ Ultra-WBG 5.5
>5 Cl) ...... - 4.8 >-El 4 Cl) C: w
-
3.3 3.4 Q. 3 n, -C)
"O C: n, 2 co
-
1.12 1.4
1 -
0 I I I I I I I
Si GaAs 4H-SiC GaN J3-Ga2O3 C AIGaN/AIN
A Closer Look: SiC vs. Si
6To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
SiC out-performs Si on 5 different parameters, lending itself to high-power, high-temperature, and fast-switching applications
Overview
0 < CD
< co :E
Electron Saturation Velocity
[x107 cm/s]
Fast Switching Applications
Melting Point [x1000 °C]
-- - ----------------,
High Temperature Applications
Electric Field [MV/cm]
E si 1- 4H-SiC
Thermal Conductivity [W/cm/°C]
•
A Closer Look: GaN vs. SiC vs. Si
7To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
To date, GaN’s upper limit on voltage rating is dictated primarily by device degradation/reliability issues
Overview
0 < CD
< ro ~
Electron Saturation Velocity
[x107 cm/s]
Fast Switching Applications
Melting Point
[x1000 °C]
Bandgap Energy ~-[eV] ~ '9~~
High Temperature Applications
~~- 0/4 ~ C"~
' '
Q>~. '9& 0~ ~
Electric Field [MV/cm]
- Si - 4H-SiC - GaN_j
Thermal Conductivity
[W/cm/°C]
•
A Closer Look: RF Performance
• RF power amplifiers are critical for radar and communications systems– Choice of semiconductor material will
depend in part on power and frequency needs
• Plot on left is intended only to provide a general idea of the capabilities of each material
8To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
DiamondGa2O3
GaN
Out
put P
ower
Frequency
SiC
InPGaAs Si
Future RF amplifiers may combine different semiconductor technologiesfor system optimization
Overview
0 < (1)
< ro :E
L.. Q)
~ 0
Cl.
•
Frequency
• Reduced current for the same power– Smaller-gauge harnesses/cabling
• Decreased design complexity – Reduced need for device stacking
• Smaller, lighter passive circuit elements
• Smaller, lighter cooling elements
9To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
Higher Blocking Voltage: Faster Switching Speeds & Lower Losses:
Toyota estimates 80% volume reduction of Prius power control unit using SiC vs. Si
https://newsroom.toyota.co.jp/en/detail/2656842 (Image used with permission)
NASA Solar Electric Propulsion:2.7 tons mass savings by moving to higher voltage power management & distribution
Source: Mercer, AIAA 2011-7252; Image: NASA
Wide-Bandgap Technology Overview:Translation of Properties into Performance
High Power Density:• 5x – 10x smaller footprint for
RF power GaN vs. GaAs• Easier impedance matching
– lower circuit losses
Ka-band power amplifier: 72% area reduction & 4x power increase using GaN vs. GaAsImage modified from: Kong, K. et al., IEEE CSICS, 2014
Overview
•
Power module
Wide-Bandgap Technology Overview:The Space Radiation Environment
• Trapped radiation belts– High & variable flux of protons and
electrons– Concerns include:
• Total ionizing dose (TID)• Displacement damage dose (DDD)• Proton-induced single-event effects (SEE)
• Solar Particle Events (SPE)– Intermittent high flux of moderate-
energy protons, electrons, and ions with atomic number Z = 1 to ~26
– Concerns include TID, DDD, and SEE• Galactic Cosmic Rays (GCR)
– Low flux of very high energy ions of all Z
– Primary concern = SEE
10To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
TID, DDD, SEESEE
TIDDDD
Image modified from:
Overview
0 < Cl)
< ro :E
•
Wide-Bandgap Technology Overview:“But I Heard that WBG Semiconductors are Rad-Hard!”
• “Inherent” radiation hardness of WBG semiconductors typically refers to their tolerance of total dose:– Both the ionization energy and threshold energy for defect formation (atomic bond strength)
exceed that for Si• Must also consider the material density (interaction cross section)
– Early WBG devices did not have gate oxides– For the same working voltage range, SiC and other doped WBG materials can have a higher
doping concentration to decrease sensitivity to carrier removal– Operation of WBG devices at high temperature results in greater mobility of defects, reducing
formation of defect complexes
11To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
Overview
0 < CD
< c;;· ~
•
SILICON CARBIDE POWER DEVICE RADIATION EFFECTS
12To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
•
SiC Outline
• Effects of radiation:– Displacement damage dose
• Diodes, JFETs
– Total ionizing dose• MOSFETs
– Single-event effects• Diodes, MOSFETs
• Radiation hardness assurance (RHA) guidance for risk-tolerant applications
• RHA considerations: looking forward
13To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
4H-SiC
6H-SiC
Davidsson, New J. Phys. 20 (2018) 023035Used with permission.
WBG
RH
A
~ co G)
::0 I )>
B,k
C,h
B, k
A,h
0 1
• B, k2
C
C, kl
A,h
C, k2
B, kl
A,h
Silicon Carbide:Displacement Damage Dose Effects
• SiC Schottky diodes are DDD-robust– Most mission DDD(Si) levels are << 1010 MeV/g – Europa Clipper is one exception at
1.7∙1010 MeV/g*• (Green dashed vertical line on plot)
14To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
Modified from: Harris, IEEE REDW, 2007
*Europa Clipper DDD(Si) behind 100 mil AlFrom: JPL D-80302, Aug 18, 2016.
SiC Schottky Diode Performance with Dose
WBG
RH
A
~ OJ G)
::a I )>
3.0
...... ~ 2.5 <(
1ij 2.0 Cl) C) n, ~ 1.5 0 > 'E 1.0
~ ~ 0.5
-
-
-
-
-
-
0.0 1010
• I I --•- SiC: CSD10030A •
-•-SiC: CSD10120A -
-
• I -• • •• I -I • •-•-•-•·•· • I / • . • •-•-· •
I -I I I
I
1011 1012
Displacement Damage Dose [MeV/g]
Silicon Carbide:Displacement Damage Dose Effects
• SiC Schottky diodes are DDD-robust• Schottky barrier diodes (SBD) may be
more tolerant than junction barrier diodes (JBS)– Most commercial SiC Schottky’s are JBS
• Protects the Schottky barrier from the high field achievable with WBG materials
15To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
Luo, IEEE TNS, 2004
SiC SBD vs. JBS
WBG
RH
A
~ CD G)
:::0 I )>
,...., N
I
E 0 I
<( ...... ~ ti) C: (1)
C ..., C: (1) ... ... ::::, u
102
10°
10·2
104
10-6
10-8
1 o -1 0
-1 0
• ---· ----
SBD pre •·-0-·· SBD post • - - JBS pre
ODD= 1.9x1011 MeV/g - •- JBS post
1 2 3 4 5 6 7 Forward Voltage [V]
Silicon Carbide:Displacement Damage Dose Effects
• SiC Schottky diodes are DDD-robust• Schottky barrier diodes (SBD) may be
harder than junction barrier diodes (JBS)• Direct comparison with Si is difficult
– Harris, 2007 showed carrier removal rate in SiCSchottky diodes was higher than in Si Schottkys, suggesting Si more DDD tolerant
• Comparison was of 4H-SiC JBS vs. Si SBD– Si PiN diodes were least DDD tolerant as expected
(minority-carrier device)• Higher-voltage rated devices were less tolerant• At higher temperature, SiC removal rate may be
reduced (see Lebedev, Semiconductors, 2002)
16To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
Modified from: Harris, IEEE REDW, 2007
Are Si Schottky’s more DDD tolerant than SiC or is the difference due to device structure and voltage rating differences?
Si vs. SiC
WBG
RH
A
~ 0) G)
:::0 I )>
3.0 ,..... ~ 2.5 <( -
I
I * I
-•- SiC JBS (300V) : -•- SiC JBS (1200V) 1 * -<>- Si SBD (150V)
•
: / -A- Si SBD (60V) 1u 2.0 1 * - • - Si PIN (1600V) & ;I
O - 0 - Si PIN (1200V) •
~ 1.5 *• / / 0 I / ~ • > o •• I 'E 1.0 ;,....:::::...._1-----•--•-•-•-•·• • .,i ~ I • •-•-• 0 .... Ah-• u. 0.5 l-----!----<'.~--~--0~ -v-v..,
t----+---.c.•---.c.~---.c.-A-A-A·A-A I
0.0 ---·=---~~~~------------1 1010 1011 1012
Displacement Damage Dose [MeV/g]
•
Silicon Carbide:Displacement Damage Dose Effects
• Impact of DDD is temperature dependent:– DDD effects in SiC reduced when measured
at 300°C • In agreement with Lebedev’s 2002 work suggesting
reduced carrier removal rate at higher temperature– Primary effect is donor compensation
• Impacts transconductance, pinch-off voltage, and on-state resistance
17To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
Modified from: McGarrity, IEEE TNS, 1992
SiC DDD tolerance increases with temperature, and SiC can operate at these high temperatures
JFET Performance with Dose at 25 °C and 300 °C:
WBG
RH
A
~ OJ G)
::0 I )>
.. -······ .... 0 ••·
0 5
---------------------
10 15 20 Drain Voltage M
50 -.------...,.....~~-.-~~~~~-~ ............. --prerad
< E ....
40
c 30 Cl) ... ... ::::, U 20 C: "§ C
10
- - - 2x1012 MeV/g
•····· 2x1013 MeV/
300 °C
.. ···· .... -······
.. --······· .. • ···················· ....
. ...
0 +-~~~~~-~~-.-~~~~ ~-~........-t 0 5 10 15 20
Drain Voltage M
•
Silicon Carbide:Displacement Damage Dose Effects
• SiC DDD tolerance depends on polytype– Comparison of 4H- and 6H-SiC JFETs from
Popelka (2014) and McGarrity (1992), respectively, suggests 6H-SiC more tolerant
– Lebedev, JAP 2000, shows that defect behavior differs between 4H- and 6H-SiC:
• Uncompensated donors increase with radiation in 6H-SiC but decrease with 4H-SiC
– McGarrity (1992) calculated a carrier removal rate ~3x lower than Si, suggesting 6H-SiC more DDD tolerant than Si
• Apparent discrepancy with Harris (2007) findings regarding SiC vs. Si may be due to polytype
18To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
Modified from: McGarrity, IEEE TNS, 1992; and Popelka, IEEE TNS, 2014
6H-SiC JFET vs. 4H-SiC JFET
For most missions, DDD in SiC will not be a concern. Actual DDD performance depends on device structure, polytype, and application temperature.
Green dashed line: Europa Clipper DDD(Si) behind 100 mil AlFrom: JPL D-80302, Aug 18, 2016.
WBG
RH
A
~ o::J G)
::0 I )> 1.1 ....-----.-................... ,...,.,..._____,----,-......,..,........,-......--.......... ~_ ..... ~~---~-...... _ ...... _ ...... _ ..... ~ ......
a> 1 -IJ- 4H-SiC 9m Uc: I -4- 6H-SiC g m I ____ m
...., 1.0 ;t. - ~ I t---------c---lJ ~4
~ 0.9 \
~ IJ I- 0.8 "C Cl)
-~ m E 0.1 ... 0 z
0.6-+-----.-................... ,...,.,...___.._,----,-......,..,........,-......--.................... ~---.-...................... ...-1
109 1010 1011 1012 1013
~---Displacement Damage Dose [MeV/g]
•
Silicon Carbide:Total Ionizing Dose Effects in MOSFETs
Despite thick oxides, SiC MOSFETs can be TID-robust:
• Cree Gens 1 & 2 in spec up to 100 krad(Si) – Above 300 krad(Si), significant gate-drain capacitance
changes can strongly impact switching performance
• Expect variability between manufacturers and processes– Hole trapping depends strongly on NO anneal time
and temperature– Interface state formation with radiation can vary– Substantial fundamental differences between radiation
responses of Si and SiC MOSFETs found via electrically detected magnetic resonance (EDMR)
TID hardness is coincidental and may change
19To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
Plots modified from: Akturk, IEEE TNS, 2012
CRSS
OrbitApprox.
1-year TID[kradISi)]
Europa Clipper 300*
GEO 150
Polar LEO 5
ISS LEO 1*100-mil Ta shielding perJPL D-80302, 8/18/2016
WBG
RH
A
~ OJ G)
::0 I )>
Li:' .s Cl) c.> C _e 0.1 ·u Ill Q. Ill u
~ Cl)
CJ Ill .. 0 > 'ti 0 .c 1/) Cl) .. .c I-
.!: Cl) CJ C Ill .c u
0
-1
-2
-3
-4
-5
-6 0 500 1000 1500
Total Ionizing Dose [krad(Si)]
o prerad a 300 krad(Si) 1::,. 600 krad(Si)
0.01 +---~--~--~-~--~-~ 0 10 20 30 40 50
Drain-Source Voltage [VJ
•
Silicon Carbide Schottky Diodes:Single-Event Effects
• SEEs in SiC Schottky diodes include:– Transient charge collection– Permanent increased leakage current– Catastrophic single-event burnout (SEB)
20To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
Kuboyama, IEEE TNS, 2006
Kuboyama, IEEE TNS, 2006
NASA GRC: A. Woodworth, 2015
WBG
RH
A
~ OJ G)
::0 I )>
I I
·.x I
I I
Region 3
F ~- ·1· -------------~::;:~ ~ --~"/-· ;---------------~ 5 I Q)U I ~ I I
I I
--------------------------- T--r---
~ Q) ..., Ol (.) .... Ql ca = .c ou u
Region 1
Bias Voltage [VJ
1 I I I I I I I I I I I I I
•
Silicon Carbide Schottky Diodes:Single-Event Effects – Thresholds
• Onsets for ion-induced leakage current and single-event burnout saturate quickly with linear energy transfer (LET)– Saturation occurs before the high-flux iron knee of the GCR spectrum
21To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
Witulski, IEEE TNS, 2018
Typical risk-avoidant mission LET requirements for SEB are > 40 MeV-cm2/mg
WBG
RH
A
~ Cl) G)
::0 I )>
Thresholds 1200 ~~-:;:--:;;-~--.,_ -= -= ~"" ..:..:." :.:....:.~ =.:::.'v':. '..:....:..~ =~ ~~~ =-- ~~~~~~~:::l
1000
-2:. aoo Q)
en 600 ro :!::
g 400
200
00
103..-------:----;------;----,---,--Fcs~ol;:ar:'."-:m~i~ni:m~um:::::===n
102
..... 101
'>. 10° "' "C 10·1
N
·e 10·2
~ 10.J
~ 104
u. 10.s
~ 10-6 Cl
"Iron Knee": max LET(Si) =
29 MeV-cm2/mg
,e 10·7
c: 10-a ~:::._- _----,-ln...,.te_rn_a-::-tio-na-;-l-;;;;Sp::--::a~ce::-;S:;::ta::;;tio::::::-n I- Polar
100-mil Al shielding
10·9 I ~1-==;:::~ ~Ge~o~st~at;::::io9na=ry;::::::;=::::;:::=;:=a.=r~::::--"---:r:::----:~-=-::;:-' 1 o -10 -F
0 1 0 20 30 40 50 60 70 80 90 100
Linear Energy Transfer (Si) [MeV-cm2/mg]
•
Silicon Carbide Schottky Diodes:Single-Event Effects – SEB
• Prior degradation can impact SEB susceptibility, interfering with identification of “SEB safe operating area (SOA)”– At a given reverse-bias voltage (VR), ion-induced leakage current (IR) can impact SEB
susceptibility if SEB does not occur early in the beam exposure• Can’t obtain “highest passing VR” and “lowest VR for SEB” within the same device
22To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
Witulski, IEEE TNS, 2018
Thresholds for SEB have uncertainty:at VR = 485 V, after <104 Xe/cm2, IR = 10 mA with non-linearity of ∆IRbefore that. Is this fluence adequate to rule out SEB? (No)
Witulski, IEEE TNS, 2018
Adequate heavy-ion test fluence levels are difficult to obtain
WBG
RH
A
• Thresholds 10 1200 - Ion, Bias
1000 - Xe, 475V
~ 8 - Xe, 485V
co -G) > 800 ~ - <(
:::0 QJ E 6 I Ol 600
._..
)> ro .... .:!::::!
C
0 ~ 4 > 400 - ... :::J u
200 2
00 00 50 100 150 200
Time (s)
Silicon Carbide Schottky Diodes:Single-Event Effects – Leakage current
Ion-induced leakage current (IR) findings:• Linearly increases with fluence (independent of flux)• ∆IR depends on
– Applied bias voltage– Ion energy deposition (linear energy transfer (LET))– Ion angle of incidence
23To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
Kuboyama, IEEE TNS, 2006 Javanainen, IEEE TNS, 2017
Heat map of ∆IRon log scale: bias and angle dependence with 1217-MeV Xe
Leakage current at 200 V as a function of ion fluence and bias during irradiation
RHA in SiC is challenging: 1) Safe Operating Area to avoid SEB is difficult to identify;2) Non-catastrophic degradation effects on lifetime reliability are unknown
WBG
RH
A
~ CD G)
:::0 I )>
~ .s i: 2! :i ()
<ll C> <1l ~ <1l <ll ...J
al Cl)
<1l 2! (.)
.5
1400
1200
1000
800
600
400
200
0 0 1x104
~ .. • 150V ~
:>
• 145V
e 140V
• 13sv
• 130V
2x104 3x104 4x1a4 5x104 6x1a4
Fluence[particle/dev]
• -340 -7
-320 -8 .:r E
-300 .9 (.)
<t e g ·10 -280 ~ e!
-11 -260 6
'j;j 12 1 -240
~ -13
-220
-14
·200 •40 ·20 0 20 40
anale l°l
Silicon Carbide MOSFETs:Single-Event Effects
24To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
SiC MOSFETs exhibit complex effects from heavy ions
• Catastrophic failure or degradation shown in drain and gate currents (ID, IG) during 10 MeV/u Xe irradiation– Results shown are for a 1200-V device
• At all biases above VDS = 50 V, part fails post-irradiation gate stress (PIGS) test – At low VDS, PIGS outcome is dependent on ion fluence
Increasing Drain-Source Voltage (VDS), with Gate-Source Voltage (VGS) = 0V
WBG
RH
A
~ co
~ G')
::0 ... C
I QI ... )>
... :I (J
10·1
10·2
10-3
104
10-S
10-6
10·7
10.a
10·9
10-10
10-11
--Drain Current - - - Gate Current
(abs. value)
10 MeV/u Xe Flux = 20 cm·2s·1
0 VGs• 600 V05
____ ,,,,,---------· --------· \, 10-12 .._ _________ ...,... _____ _
-20 -15 -10 -5 0 5
Elapsed Time [s]
10 MeV/u Xe
-4 Flux = 6 cm·2s·1
~ 2x10 0 VGS• 500 Vos ... C
~ :I
u 1x104
o- - - - ---------------------20 0 20 40 60 80
Elapsed Time [s]
100
1.0x10"6
5.ox10·1
0.0 - --- - ..
-5.0x10·7
.. .. .. .... .... 10 MeV/u Xe
·1,ox10-6 Flux = 1500 cm·2s·1
0 VGs• 300 V05
-1.5x10"6+----------.-------...---...
10-s
~ 10-6 ... C QI 10-7 ... ... :I (J
~ 10.a Ill ~ Ill
10·9 QI ...I QI ... ~ 10-10
-20 0 20 40
Elapsed Time [s]
a Spec/
10 MeV/u Xe: 100 Vos
Slope = 1.3x10·13
Cl a CIC
Cl
a
0
oOO 0
0
10 MeV/u Ar: 300 V05
Slope= 2.6x10·15 10-11-+---~~---~--~----........f
102 103 104 105
Fluence [cm-2]
•
SiC MOSFET Effects as a Function of VDS at VGS = 0 V:Latent Gate Damage
25
Dra
in-S
ourc
e Vo
ltage
Q Collection
During Irradiation Post Run
Measurement Results
No Measurable Effect
IGSS ↑Q Collection
Voltage range of no effects (grey) or only latent damage (change in PIGS test: green) is a function of ion/LET, device voltage rating, and manufacturer/generation
Grey = no ion effects;Green = VDS range for which only latent damage occurs
To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
WBG
RH
A
1500
~ 10• 1400
co a 0
G) 10• "
_,, 1300
::0 10J 1200
I 10•
)> 10 MeWu Xe: 100 V05
10• S!ope • 13x10'11
a" oOO a" 0
10•ID a 0 10 MeV/u At: 300 VD!
s;-1100 -OJ 1000 tl.O
10'H Slopes:26x 10'tS
10' 10' 10• 10• 10•
ro 900 +-'
Ftuence (cm4) 0 > 800 Q) u 700 lo.. :, 0 600 V')
-----------• I
C 500 ro lo..
0 400
300
200
100
0 Device:
Ion/LET:
I • No Effect
- - - - - -
--
t---
--- --
--
--
--
--
Ml
B 0.9
-
t---
M2 M7
Ar 8.9
-- --
-- --
t---
--
-- --
Ml
Arl0
(to 3300)
Latent Gate Degradation I
-
--
-M2 M3
Cu 23
--
--
--
--
--- -M4 MS
Ag47
--
--
--
--
- - -M2 M3 M4 MG M7 MS
Xe 63
•
SiC MOSFET Effects as a Function of VDS at VGS = 0 V:Latent Gate Damage
26
Dra
in-S
ourc
e Vo
ltage
Q Collection
During Irradiation Post Run
Measurement Results
No Measurable Effect
IGSS ↑Q Collection
No latent damage to gate from low LET/light ions
Grey = no ion effects;Green = VDS range for which only latent damage occurs
To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
WBG
RH
A
10•
~ a 0 10• " co
_,, G')
10J
::0 10•
10 MeWu Xe: 100 V05
I 10• S!ope• 13x10'11
)> a" oOO a" 0
10•ID a 0 10 MeV/u At: 300 VD!
10'H Slopes:26x 10'tS
10' 10' 10• 10• 10•
Ftuence (cm4)
-----------•
1500
1400
~ -------------------------- (to 3300)
1300
1200
s;-1100 - ~ ~~~...._
g Q) u lo.. :, 0
V') I
C ro lo..
0
100
0 Device: Ml
Ion/LET: B 0.9
• No Effect
M2 M7
Ar 8.9
Ml
Arl0
Latent Gate Degradation
M2 M3
Cu 23
M4 MS
Ag47
M2 M3 M4 M6 M7 M8
Xe 63
•
SiC MOSFET Effects as a Function of VDS at VGS = 0 V:Latent Gate Damage
27
Dra
in-S
ourc
e Vo
ltage
Q Collection
During Irradiation Post Run
Measurement Results
No Measurable Effect
IGSS ↑Q Collection
Onset is independent of MOSFET voltage rating and manufacturer/generation at higher LETs
Grey = no ion effects;Green = VDS range for which only latent damage occurs
To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
WBG
RH
A
10•
a 0 10• "
~
_,, 10J
co 10• G) 10 MeWu Xe: 100 V05
::0 10• S!ope• 13x10'11
a" oOO
I a" 0 10•ID a 0 10 MeV/u At: 300 VD! )> Slopes:26x 10'tS 10'H
10' 10' 10• 10• 10•
Ftuence (cm4)
-----------•
1500
1400
~ -------------------------- (to 3300)
1300
1200
s;-1100 -OJ 1000 tl.O
2 900
g 800 Q)
~ 700 :, o 600
V') I
C 500 ro ,_ o 400
300
200
100
0 Device: Ml
Ion/LET: B 0.9
• No Effect
M2 M7
Ar 8.9
Ml
Arl0
Latent Gate Degradation
•
MOSFET Effects as a Function of VDS at VGS = 0 V:Degradation During Beam Run
28
Dra
in-S
ourc
e Vo
ltage
Q Collection
During Irradiation Post Run
Measurement Results
No Measurable Effect
IGSS ↑Q Collection
Not all MOSFETs exhibit drain-gate leakage current degradation:Design techniques may eliminate this vulnerability
Yellow = VDS range for ∆ID = ∆IG degradationGreen = VDS range for which only latent damage occurs
↑ IDG∆ID = ∆IG
IGSS , IDSS ↑;Failed IGSS
Color gradients span between
known VDSfor given
response types
To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
WBG
RH
A
~ co G')
::0 I )>
·······~ . 1,0X1 0
5.0x10 -1
··•"--- ~
-1 .0xtO,. :~~~~ecn,·~ ·•
.. .. ....
0 Vos, 300 Vos -t.Sxto•+---~-~----
-20 0 20 •• E13psed Time [s)
i -----------•
-----------•
1500
1400
1300
1200
s;1100 -OJ 1000 tl.O ro 900 ...... 0 > 800 Q) u 700 .... :::, 0 600 V)
I
C 500 ro .... 0 400
300
200
100
0 Device :
Ion/LET:
(to 3300)
I • No Effect Latent Gate Degradation D ld=lg I
- - - - - - -
----
--
--
--
--
Ml
B 0.9
f----
-
M2 M7
Ar 8.9
--
--
-- --
-- ---
--- --- --
Ml @ M3
Ar 10 Cu 23
--
--
--
--
f----
--
-
M4 MS
Ag47
--
--
-- --
- f---- -
M2 M3 M4 MG M7®
Xe 63
•
MOSFET Effects as a Function of VDS at VGS = 0 V:Degradation During Beam Run
29
Dra
in-S
ourc
e Vo
ltage
Q Collection
During Irradiation Post Run
Measurement Results
No Measurable Effect
IGSS ↑Q Collection
IDS degradation least influenced by electric field and ion LET: linked to material properties??
Blue = VDS range for ∆ID >> ∆IG degradationYellow = VDS range for ∆ID = ∆IG degradation
↑ IDG∆ID = ∆IG
IGSS , IDSS ↑;Failed IGSS
↑ IDG, IDS∆ID >> ∆IG
IDSS ↑;↑ or Failed IGSS
Color gradients span between
known VDSfor given
response types
To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
WBG
RH
A
~ co G)
::0 I )>
:S.0ll 10""' - 10
2.lb:10" •••• la
SOOVir,5 2..0:1:10"' ~ Mev:xe
Ave. Flux: 6 cm4 1-·1
1.&:-10 ...
1.0:ic 10 ...
0.0
... .. Elap$ed Time (•)
i
100
i
-----------•
i i -----------•
-----------•
1500
1400
1300
1200
s;1100 -OJ 1000 tl.O .g! 900
g 800 Q) u 700 .... :::, 0 600 V)
I
C 500 ro .... 0 400
300
200
100
0 Device :
Ion/LET:
~ ------------------------ (to 3300)
• No Effect
M l M 2 M 7
B 0.9 Ar 8.9
La t ent Gat e Degradation • ld=lg • ld>lg
M l M 2 M 3
Arl0 Cu 23
M4 MS
Ag47
M2 M3 M4 M G M7 MS
Xe 63
•
MOSFET Effects as a Function of VDS at VGS = 0 V:SEB/GR
30
SEB/GR vulnerability at LET(Si) < 1 MeV-cm2/mgVulnerability saturates before the GCR flux “iron knee”
Red = VDS range for SEB/GRBlue = VDS range for ∆ID >> ∆IG degradationYellow = VDS range for ∆ID = ∆IG degradation
Color gradients span between
known VDSfor given
response typesDra
in-S
ourc
e Vo
ltage
Q Collection
During Irradiation Post Run
Measurement Results
No Measurable Effect
IGSS ↑Q Collection
↑ IDG∆ID = ∆IG
IGSS , IDSS ↑;Failed IGSS
↑ IDG, IDS∆ID >> ∆IG
IDSS ↑;↑ or Failed IGSS
Suddenhigh-I event
Catastrophic Failure:BVDSS < 2 V
SEB
/GR
ons
et n
ot fo
und
To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
WBG
RH
A
-----------•
i i
-----------•
i i -----------•
-----------•
1500
1400
1300
1200
s;1100 -OJ 1000 tl.O ,g! 900
g 800 Q) u 700 .... :::, 0 600 V)
I
C 500 ro .... 0 400
300
200
100
0 Device:
Ion/LET:
~ ------------------------ (to 3300)
Ml
B 0.9
D No Effect Latent Gate Degradation D ld=lg • ld>lg • SEE
M2 M7 Ml
Ar 8.9 Arl0
M2 M3
Cu 23
M4 MS
Ag47
M2 M3 M4 MG M7 MS
Xe 63
•
• Reduced SEB/GR susceptibility– Thicker epilayer
SiC Radiation Hardness by Process: 1200 V MOSFET
31
Just as with silicon MOSFETs, epilayer optimization must be done to balance SEE tolerance with on-state resistance (RDS_ON) performance
Color gradients span between
known VDSfor given
response types
To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
After Zhu, X., et al., 2017 ICSCRM
WBG
RH
A
• 1500
1400 D No Effect • Latent Gate Degradation • ld=lg • ld>lg • SEE
1300
1200
~1100
Q) 1000 tl.0 ro 900 +-'
g 800 Q) u 700 ,._
~ =, 0 600 co V)
G) I
C 500 :::0 ro ,._ I Cl 400 )>
300
200
100
0 Device: Baseline Modified
Ion/LET: Ag47
• Reduced SEB/GR susceptibility– Thicker epilayer
• Degradation of IDG eliminated – Drain neck width reduction
SiC Radiation Hardness by Process: 1200 V MOSFET
32
Elimination of drain-gate leakage current degradation mode is possible through established silicon MOSFET hardening techniques
Color gradients span between
known VDSfor given
response types
To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
After Zhu, X., et al., 2017 ICSCRM
WBG
RH
A
• 1500
1400 D No Effect • Latent Gate Degradation • ld=lg • ld>lg • SEE
1300
1200
~1100
Q) 1000 tl.0 ro 900 +-'
g 800 Q) u 700 ,._ =,
~ 0 600 V)
I
OJ C 500 G) ro ,._ ::0 Cl 400 I
300 )>
200
100
0 Device: Baseline Modified
Ion/LET: Ag47
• Reduced SEB/GR susceptibility– Thicker epilayer
• Degradation of IDG eliminated – Drain neck width reduction
• Minimal change in onset of other degradation effects:– ∆ID >> ∆IG– latent gate damage
• Rate of degradation at a given voltage is reduced
SiC Radiation Hardness by Process: 1200 V MOSFET
33
Continued research and development efforts are necessary to understand residual degradation mechanisms!
Color gradients span between
known VDSfor given
response types
To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
After Zhu, X., et al., 2017 ICSCRM
WBG
RH
A
1500
1400
1300
1200
~1100
Q) 1000 tl.0 ro 900 +-'
g 800 Q) u 700 ,._ =, 0 600 V)
I
~ C 500 Cl) ro ,._ G) Cl 400
::0 300 I )> 200
100
0 Device:
Ion/LET:
D No Effect • Latent Gate Degradation • ld=lg • ld>lg • SEE
.....,_._._..,.,,.. ... ,_ -_ -_ -_ -_ -_ -_ -_ -_ -_ ..... ---1
~==========1 • Baseline Modified
Ag47
•
Normalized Onset Voltage for Immediate SEB/GR: Comparison of Device Types
34
Measurable onset for SEB/GR similar across device types: ~40% to 50% of rated VDS
Must derate below this level to account for SEB/GR SOA uncertainty
To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
WBG
RH
A
1.0
0.9
0.8 Q)
g> 0.7 ~ 0 0.6 >
"C 0.5 Q)
.!::! n, E
0.4 '- 0.3 0
~ z co 0.2 G)
:;o I
0.1
• 0.0 0
SEB/GR: 'ff MOSFET 0 Schottky Diode
• JFET ~ PIN Diode
I i
5 10 15 20 25 30 35 40 45 50 55 60 65 70
Linear Energy Transfer (Si) [MeV-cm2/mg]
•
Comparison of SEB/GR Susceptibility Across SiC Power Devices: Neutron Data
35To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
The data strongly suggest that for SEB/GR, the electric field strength is driving the susceptibility; there is no indication of a different mechanism
involved for the different device types.
Used with permission from: CoolCAD Electronics (left), Wolfspeed (right)
Terrestrial neutron failures-in-time (FIT) data normalized to the active die area, as a function of bias voltage normalized to measured avalanche voltage.
WBG
RH
A
~ OJ G)
::0 I )>
. . X ........ ...... ....... ; ... ....... ..... ...... ; ...... ,. ... ....... . .
(1) :X •• ,,,,,,, .......... ,,,,!••·················••:- ••·················· ~ 103
cu • .... , (1) • ,, ... .
Cl) . , , .
IA\ 102 , . , . . . , ... , ... . ... . .. j, .. ~ ... ,t,,, .• '. . . . . ; .. ... ... . . . . ....... , v:::!I . , •
N !.a.. • : 5 101
........ . .......... t F, ........ • Wolfspeed 1700 ~ ,,.. .a. !. X STMicro 1200V u. w O Rohm 1200V
1 o0 ........... .. ...... ; .......... • Microsemi
.
0.4
.a. Wolfspeed 1700
0.6 0.8 BiasN
1 (VN)
ava
10000
1000
N 100 E u t:: 10 LL
1
1 0.1
Sea-level Neutron FIT/cm2
0 .3 0 .4 0.5 0.6 0. 7 0.8 0.9 1.0 1.1
Vo/ Vaval
•
RHA Guidance• SEB/GR safe operating area (SOA) is difficult to reliably define
– Susceptibility quickly saturates before the high-flux iron knee of the GCR spectrum• (Unvalidated) failure rate prediction methods developed for Si power devices may
provide an upper bound– Degradation of gate/drain leakage currents hides onset bias for SEB/GR at all but lowest LETs
• For risk-tolerant applications, margin and unpowered redundancy is advised
• Non-catastrophic damage has unknown longer-term effects – Extent of damage is part-to-part variable– Consider application temperature and functional lifetime requirements
• For risk-tolerant applications, margin and unpowered redundancy is advised– Life tests of damaged parts may reveal higher-likelihood failure modes - sample size will limit
discovery of rarer modes • Remember to consider other non-RHA concerns:
– There are no space qualification standards specific for WBG technologies
36To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
WBG
RH
A
~ c:o G)
:::0 I )>
ObscrT cd Failun:
=· Const.int (Ran d om)
Failures
•
.. ·· C:ilr'Out
Failures
••••• . I I
· ··· •• J ••••• • ••••••• •• ••• •• ••••• ••• ( ••••• ••••••• •••••• t
Time
SiC RHA Considerations• There are limited efforts underway to develop radiation-hardened SiC power
devices – Some degradation mechanisms may persist despite RHBD efforts– Impact on device long-term reliability must be established
• Radiation hardening comes with a cost– As with Si power MOSFETs, electrical performance will suffer from hardening techniques
• Testing with lighter ions/lower LETs will reveal nuances between designs and aid on-orbit degradation predictions– Responses are saturated at LETs dictated by typical mission destructive-SEE radiation
requirements– LET should be specified in terms of LET(Si) but penetration range must be for SiC
• Characterization data should include identification of voltage conditions at which different effects occur– Richer dataset will include how susceptibility to these effects changes with ion
species/LET/angle/temperature
37To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
WBG
RH
A
V ~ OJ C)
:;o I )>
I
•
GALLIUM NITRIDE HIGH ELECTRON MOBILITY TRANSISTOR (HEMT) RADIATION EFFECTS
38To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
WBG
RH
A
/' ~ OJ G)
::0 I )>
I
•
GaN HEMT Outline
• Introduction to GaN high electron mobility transistors (HEMTs)
• Effects of radiation:– Displacement damage dose– Total ionizing dose– Single-event effects
• RF GaN HEMTs• Enhancement-mode HEMTs
• Radiation hardness assurance guidance
39To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
Images: NASA JPL, courtesy of L. Scheick
SEE failure sites (ex/ right photo) superimposed onto optical image (left) suggest random distribution
WBG
RH
A
V ~ CD G)
:::0 I )>
•
GaN HEMT Introduction: Device Structure
• Two primary flavors of GaN HEMTs: – Depletion mode (normally on)– Enhancement mode (normally off)
• Normally-off GaN is achieved in several ways:– Cascode with a low-voltage normally-off silicon
MOSFET• Penalty to RDS_ON lessens with higher voltage-rated
GaN HEMTs– p-doped GaN gate
• Used in first commercial eGaN devices• Gate built-in voltage exceeds piezoelectric field
– Recessed Schottky gate• Thinned AlGaN barrier beneath gate to reduce
piezoelectric voltage below Schottky built-in voltage– Flourine-implanted AlGaN barrier
• Traps negative charge in the layer
40To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
Typical GaN HEMT structure sets up lattice strain and charge polarization between the AlGaN
barrier and GaN layer, creating a 2-dimensional path for electrons to flow
Energy band diagram showing 2-D electron gas formation (yellow)
AlGaN GaNMetalGate
ECEF
EV
Many gate designs: How will these differences affect space qualification standards development for GaN?
Substrate (SiC, Si, …)
AlN (seed layer)AlGaN Buffer
AlGaN BarrierGateSource Drain
GaN
WBG
RH
A
•
GaN HEMT Introduction: Applications
• RF GaN HEMTs– Initially, RF applications dominated due in part
to depletion-mode operation– Designed to work well in linear region for max
gain, min distortion• Characterization includes incident and reflected wave
power measurements as well
• Enhancement mode GaN HEMTs as switches– Development of normally-off HEMTs provided
in-road to power management applications• Start-up does not require an initial gate bias to be applied
to avoid short-circuit damage
– Designed to work well in on-state/transition states to minimize losses
• Low RDS_ON and off-state drain leakage current (IDSS)
41To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
Can a single set of radiation test method standards be developed for both RF GaN and enhancement-mode GaN HEMTs?
Output Signal
InputSignal
RF apps often operate in linear region
Switch apps operate along load line
WBG
RH
A
•
Gate-Source Voltage M
::f. c ~ :::,
(.) v C: -~ ~ 0 OJ
G)
::0 I )>
Drain-Source Voltage [VJ
GaN HEMTs:Displacement Damage Dose Effects
• Parametric degradation in GaN HEMTs occurs at DDD levels far above those for space applications– Weaver, et al., 2015 show order-of-magnitude
better performance of GaN vs. GaAs HEMTs– Possibly due to re-injection of
scattered carriers• GaN HEMT DDD effects include
– Decreased drain current– Threshold voltage shift (typically positive)– Decreased mobility and transconductance– Decreased power gain
42To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
Weaver et al. ECS J. Solid State Sci. Technol. 2016. Used with permission.
GaN HEMTs out-perform GaAs HEMTs
Ives, IEEE TNS 2015. Used with permission.
Power gain decreases despite correction of ∆ID
For extreme DDD environments, use of a feedback system to maintain quiescent ID will improve
radiation tolerance1.8 MeV protons
WBG
RH
A
✓
~ Cl) C)
::0 I •
1.0
c ~ 0.8 ::, ()
C
-~ 0.6 0
a1 N
~ 0.4 E 0 z
0.2
1E9
! • I "' .., t· Current
••• ~t i a J f Da7
1E10
... . • * ~· "' . • ' "' * t :]
1E11
... * "' X X
• • • • ... ... .
GaAs • GaN
1E12 1E13
Displacement Damage Dose (MeV/g)
13~---------------~
12.5
12
iii' 11 .5 :!:!. c: 11 ·;;; C> 10.5
10
9.5
• Pre
• 3x1012
1x1013
.. 3x1013
• 1x1014
?is -20 -1s -10 -s o s Input Power [dBm]
10 15
•
GaN HEMTs:Displacement Damage Dose Effects
• DDD susceptibility is greater when:– parts are biased during irradiation– parts have had prior hot-carrier stress– see Chen, et al., IEEE TNS 2015
• Radiation increases the concentration of existing defects
43To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
Pearton, ECS J. Solid State Sci. Technol. 2016. Used with permission.
Concentrations of existing defects increase with radiation exposure
GaN HEMT DDD effects: 1) Bias matters during irradiation
2) Prior hot-carrier stress can enhance radiation effects3) There is significant variability of response to radiation
WBG
RH
A
~-0.13ev, E -0.16eV-. Ec-0.60eV
E -0.71eV
n-GaN:Si p-GaN:Mg
+3.28eV
----Ev+3.00eV
Ey+2.42eV
---- - Ev+1 .50eV
E -3.25eV ~===~~---- EF VB
/' ~ OJ G')
::0 I )>
as-grown traps irradiation-induced traps
•
• Many gate designs:• RF GaN HEMTs (Schottky gate)
– Aktas, 2004 demonstrated 0.1 V threshold shift after 6 Mrad(Si) γ irradiation
– Harris, 2011 demonstrated no significant shift after 15 Mrad(Si) proton irradiation
• p-GaN gate– 500 krad(Si) γ irradiation: < 18% Vth shift (Lidow,
2011)• MOS gate
– No data– This design is most likely to be sensitive to TID
effects
44To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
GaN HEMTs:Total Ionizing Dose
Images: NASA JPL
GaN HEMT designs vary
GaN HEMT TID effects: Robust in absence of gate oxide;
To be determined for those with oxides
WBG
RH
A
V ~ OJ G)
::0 I )>
1 µm >-< EHT=1000kV
WD : 70mm
EHT • 10.00 kV
WO• 71mm
Signal A ., SESI
Mag= t0OOKX
Signal A • SESl
Mag • 3.15KX
Date .28 Apr 2016 FIB Loc:t< Mag$ ., No
o.te .2GA9{2018 F18 Lode Mags ,. No
•
111
• Catastrophic SEE:– In some parts, SEB occurs only at VDS levels above those reached during RF operation
• Rostewitz, 2013 and Osawa, 2017 tested in both DC and RF modes: Calibrated measurements of max transient VDS during RF operation showed no excursions above SEB failure threshold VDS found in DC mode tests
• Osawa, 2017 noted the failure threshold in DC mode was over 3X VDS bias level for RF mode; no failures in RF mode
• Armstrong, 2015 showed no failures in RF mode– However, some unpublished data suggest some parts/lots may be susceptible to SEB in
RF mode• Lot-lot variability found
45To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
RF GaN HEMTs:Single-Event Effects
Although generally SEB-robust, some unpublished SEB failures have occurred at biases relevant to RF operation
WBG
RH
A
/ ~ OJ G)
:::c I )>
•
• Increased leakage currents– Armstrong, 2015 study of 5 different HEMTs from 4 manufacturers revealed manufacturer and
part-part variability in susceptibility to increasing gate leakage current due to heavy-ion induced damage
– Kuboyama, 2011 study reveals two different degradation modes• At lower DC VDS bias, IDG degradation• At higher DC VDS bias, IDS degradation
46To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
RF GaN HEMTs:Single-Event Effects
All heavy-ion studies of RF GaN HEMTs report increased leakage current
ID and IG as a function of 3.5 MeV/u Kr fluence and VDSreveals 2 damage pathways
Kuboyama, 2011 IEEE TNS. Used with permission.
WBG
RH
A
/ ~ OJ G)
:::0 I ):>
lx l0-31-------------------L.;14*015~ V 8x l04
~ i: ~ 6x l04
u ~ ~ i'3 4xJ0-4 ....J
2x l04
30 40 50
0 5xl07
I Drain Current I J I~
130
90 120
100
11 0 )t:,;jent I
lx l08 Fluence [cm-2]
l.5x I os
•
• Catastrophic SEE:– Susceptibility is very wafer-lot specific
• Likely accounts for some data discrepencies in the literature• Lot-specific testing is critical
– Susceptibility can depend on test circuit design (Scheick, 2014, 2015, and 2018)• When gate is tied to the source at the part level, threshold for SEE improves
– Gate transients upon ion strikes are unrealistically dampened• Gate off-state bias level has minimal effect
– Angle effects are variable• Variability between lots of same part (Scheick, 2018)• Compounds difficulty of estimating an on-orbit failure rate
• Increased leakage currents:– Drain-source leakage current affected
47To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
Enhancement-Mode GaN HEMTs:Single-Event Effects
Lot-specific testing is critical
0 20 40 60
Angle [Deg]
0
200
400
600
800
Dra
in-to
-Sou
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(Vds
) [V
]
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NASA, courtesy L. Scheick.
Variable effect of angle on SEB susceptibility
WBG
RH
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•
RHA Guidance• Lot-specific heavy-ion testing is necessary
– Several suppliers now offer “space qualified” enhancement-mode GaN HEMTs, providing wafer lot level screening for SEE• Radiation test methods for GaN are not standardized
• Unlike for SiC, GaN SEE safe operating areas (SOAs) can be identified– Valid for the tested lot only– Part-part variability reduces confidence
• Derate, derate, derate– Ensure that all transient voltages fall within the SOA
• More data are needed on angle effects to understand worst-case test conditions– SEB SOAs to date are established with data taken at normal incidence only
• Until effects are understood, additional margin (derating) may reduce risk
• Effect of leakage current degradation on device reliability/lifetime is unknown• Remember to consider other non-RHA reliability concerns
– Hot carrier damage– Current collapse– Dynamic RDS_on
– And others48To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
WBG
RH
A
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::0 I )>
•
A GLIMPSE INTO THE FUTURE
49To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
The Future •
Qualification Standardization & Technology Maturation
• Supplier qualification data are based on standards for silicon– Methods vary between vendors
• JEDEC has established a new committee to address this need– JC-70 Wide Bandgap Power Electronic Conversion Semiconductors
• Sub-committees for SiC and GaN– Focused initially on non-radiation reliability
• Aerospace Corporation Guideline document for GaN now available– TOR-2018-00691, “Guidelines for Space Qualification of GaN HEMT Technologies”
• NASA Electronic Parts and Packaging Program RHA guidelines to be developed– Work to begin FY2019
• Funded efforts to mature WBG technologies for space application are underway– ESA Materials and Components Technology Section (TEC-QTC) programs– NASA and Dept. of Defense Small Business Innovative Research (SBIR) awards and other
grant mechanisms– Other international government and industry programs
50To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
The Future
•
The Future of SiC and GaN
Markets:• Automotive industry forecasted to drive the SiC power market
– Almost all carmakers are working to implement SiC in their main inverter– SiC transistor forecasted compound annual growth rate for 2017-2023: 50%– Source: Yole Power SiC 2018 Market & Technology Report
• Largest growth in GaN market size will be power supply applications– Over 2 orders of magnitude growth expected by 2021
• Source: Yole Power GaN 2017: Epitaxy, Devices, Applications, and Technology Trends
R&D efforts• Vertical GaN power devices for higher current and voltage• Increased GaN reliability• Increased SiC reliability
51To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
Creative Commons CC0
The Future
•
Ultra WBG: Diamond
• Benefits:– Best of everything (see plot)– High electron and hole mobilities– Electron emissivity
• Target applications: “Ultra-high power” market (1 kW or more)– Radar– Communication satellites– Vacuum electronics (driver, cathode)
• Status:– 10 mm x 10 mm wafers commercially available– Vertical SBDs, MESFETs, and MOSFETs have been
developed• Challenges for maturation
– Crystal quality and size– Absence of n-doping
52To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
The Future
Electron Saturation Velocity
[x107 emfs]
Fast Switching Applications
\ \
\
,'
' \ \
\
\
\
Melting Point [x1000 °C]
• Bandgap Energy ~ -
[eV] ~ ~~k
,'
High Temperature Applications
~~- 0/4 C' --~
<$>~. ~$ 0~
,S'
Electric Field [MV/cm]
,' - Si --4H-SiC --GaN --c
Thermal Conductivity [W/cm/°C]
Ultra WBG: Ga2O3
• Benefits:– Power-Frequency figure of merit (FOM) > 2x GaN– Specific on-resistance in vertical drift region > 10x SiC– High-quality native substrate– Wafer costs are comparable to GaN
• Target applications: “Ultra-high power” market (1 kW or more)– Radar– Communication satellites– LED market
• Status:– Least mature of the ultra-WBG technologies– 2” Wafers commercially available– Vertical SBDs, MESFETs, and MOSFETs have been developed
• Challenges for maturation– Crystal quality– Absence of p-doping; self-trapping of holes– High contact resistance– Thermal management: poor heat dissipation
53To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
The Future
Electron Saturation Velocity
[x107 emfs]
Fast Switching Applications
Melting Point [x1000 °C]
• Bandgap Energy ~ -
[eV] ~ ~~k
High Temperature Applications
~~- 0/4 C' --~
<$>~. ~$ 0~
,S'
Electric Field [MV/cm]
- Si --4H-SiC --GaN --f3-Ga20 3
Thermal Conductivity [W/cm/°C]
54To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018
Thank you for your attention!
•