https://ntrs.nasa.gov/search.jsp?R=20200003156 2020-06-17T23:19:15+00:00Z
National Aeronautics and Space Administration
Wide-Bandgap Semiconductors in Space: Appreciating the Benefits but Understanding the Risks
Jean-Marie Lauenstein NASA GSFC, Greenbelt, MD, USA
To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 1 Acronyms and Abbreviations Acronym Definition Acronym Definition Acronym Definition • 2-D Two Dimensional ID Drain Current SBD Schottky Barrier Diode
AlGaN/AlN Aluminum Gallium Nitride/Aluminum Nitride IDSS Drain-Source Leakage Current SBIR Small Business Innovative Research
BVDSS Drain-Source Breakdown Voltage IG Gate Current SEB/GR Single-Event Burnout/Gate Rupture
C Carbon IGSS Gate-Source Leakage Current SEE Single-Event Effect
DDD Displacement Damage Dose InP Indium Phosphide Si Silicon
EC Conduction Band Energy IR Reverse Current SiC Silicon Carbide Sn Tin EF Fermi Level Energy ISS International Space Station JBS Junction Barrier Schottky diode SOA State Of the Art; Safe Operating Area Egap Bandgap Energy STMD Space Technology Mission Directorate ESA European Space Agency JFET Junction Field Effect Transistor LEO Low Earth Orbit SWAP Size, Weight, And Power EV Valance Band Energy TAMU Texas A&M University cyclotron facility FIT Failures In Time LET Linear Energy Transfer TID Total Ionizing Dose FOM Figure of Merit MESFET Metal-Semiconductor Field Effect Transistor Metal Oxide Semiconductor Field Effect UWBG Ultra-Wide Bandgap FY Fiscal Year MOSFET Transistor VDMOS Vertical Double-diffused MOSFET GaAs Gallium Arsenide NO Nitric Oxide VDS Drain-Source Voltage GaN Gallium Nitride PIGS Post-Irradiation Gate Stress VGS Gate-Source Voltage Ga2O3 Gallium Oxide R&D Research and Development VR Reverse-bias Voltage GCR Galactic Cosmic Ray RDS_ON On-State Drain-Source Resistance VTH Gate Threshold Voltage GEO Geostationary Earth Orbit RF Radio Frequency WBG Wide Bandgap HEMT High Electron Mobility Transistor RHA Radiation Hardness Assurance Xe Xenon
RHBP Radiation Hardened By Process
To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 2 Outline • • Overview – Bandgaps: the simple explanation – Wide-bandgap (WBG) technology advantages & applications Overview 0 < – Space environment hazards ct) WBG RHA WBG (ac) ) I – SiC discrete power devices – GaN high electron mobility transistors (HEMTs): • RF The Future •Enhancement-mode • A Glimpse into the WBG Semiconductor Horizon – Qualification standardization & technology maturation Reprinted with permission from Yao, et al., JVSTB, vol. 35, p. 03D113. Copyright 2017, – The future of SiC and GaN American Vacuum Society – Ultra-Wide Bandgap (UWBG) semiconductors • Diamond • Ga2O3 To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 3 Overview 0 Wide-Bandgap Technology Overview: < CD Conduction Band Egap Valence Energy(E) [eV] Band • 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 To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 4 Wide-Bandgap Technology Overview: Properties Associated with the Bandgap Overview 7 • 0 < ct) ~ Conventional 6 0 I I I I I I I Si GaAs 4H-SiC GaN J3-Ga2O3 C AIGaN/AIN • WBG semiconductors can: – Operate at higher temperatures without “going intrinsic” 4 – Block higher voltages for a given thickness of material (breakdown voltage ∝ (Egap) ) – Switch at higher speeds due in part to higher saturation velocities – … and other WBG-material specific advantages To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 5 A Closer Look: SiC vs. Si • Overview 0 < CD < co Electron :E Saturation Velocity Electric Field [x107 cm/s] [MV/cm] Fast Switching Applications E si 1- 4H-SiC ------, Melting Point Thermal Conductivity [x1000 °C] [W/cm/°C] High Temperature Applications SiC out-performs Si on 5 different parameters, lending itself to high-power, high-temperature, and fast-switching applications To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 6 A Closer Look: GaN vs. SiC vs. Si • Bandgap Energy ~- [eV] ~ '9~~ ~~- 0/4 ~ C"~ Q>~. '9& 0~ ~ Electron ' ' Electric Field Overview Saturation Velocity 0 < 7 [MV/cm] CD [x10 cm/s] < ro Fast Switching ~ Applications - Si - 4H-SiC - GaN_j Melting Point Thermal Conductivity [x1000 °C] [W/cm/°C] High Temperature Applications To date, GaN’s upper limit on voltage rating is dictated primarily by device degradation/reliability issues To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 7 A Closer Look: RF Performance • L.. • RF power amplifiers are critical for Q) Diamond radar and communications systems ~ Ga O 0 2 3 – Choice of semiconductor material will Cl. SiC depend in part on power and frequency needs Overview 0 GaN < • Plot on left is intended only to provide a general (1) idea of the capabilities of each material ro< InP :E Output Power Output Si GaAs FrequencyFrequency Future RF amplifiers may combine different semiconductor technologies for system optimization To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 8 Wide-Bandgap Technology Overview: Translation of Properties into Performance • Higher Blocking Voltage: Faster Switching Speeds & Lower Losses: • Reduced current for the same power • Smaller, lighter passive circuit – Smaller-gauge harnesses/cabling elements • Decreased design complexity • Smaller, lighter cooling elements – Reduced need for device stacking Power module NASA Solar Electric Propulsion: 2.7 tons mass savings by moving to higher voltage power management & distribution Toyota estimates 80% volume reduction of Source: Mercer, AIAA 2011-7252; Image: NASA Prius power control unit using SiC vs. Si Overview https://newsroom.toyota.co.jp/en/detail/2656842 (Image used with permission) High Power Density: • 5x – 10x smaller footprint for Ka-band power amplifier: 72% area RF power GaN vs. GaAs reduction & 4x power increase • Easier impedance matching using GaN vs. GaAs – lower circuit losses Image modified from: Kong, K. et al., IEEE CSICS, 2014 To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 9 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) TID • Solar Particle Events (SPE) DDD – Intermittent high flux of moderate- energy protons, electrons, and ions with atomic number Z = 1 to ~26 – Concerns include TID, DDD, and SEE TID, DDD, SEE Overview • Galactic Cosmic Rays (GCR) 0 < SEE Cl) < – Low flux of very high energy ions of ro Image modified from: :E all Z – Primary concern = SEE To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 10 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 Overview 0 < CD c;;·< ~ To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 11 • SILICON CARBIDE POWER DEVICE RADIATION EFFECTS To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 12 WBG RHA WBG ~ co G) SiC Outline ::0 I )> • • Effects of radiation: 6H-SiC – Displacement damage dose k C • Diodes, JFETs B, 2 4H-SiC – Total ionizing dose C, kl • MOSFETs B,k A,h – Single-event effects C,h • Diodes, MOSFETs C, k2 • Radiation hardness assurance (RHA) B, k B, kl guidance for risk-tolerant applications A,h A,h • RHA considerations: looking forward 0 1 Davidsson, New J. Phys. 20 (2018) 023035 Used with permission. To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 13 WBG RHA WBG Silicon Carbide: ~ OJ G) Displacement Damage Dose Effects ::a I )> • SiC Schottky Diode • SiC Schottky diodes are DDD-robust Performance with Dose – Most mission DDD(Si) levels are << 1010 MeV/g 3.0 - I I - -•- SiC: CSD10030A – Europa Clipper is one exception at ...... -•-SiC: CSD10120A • 10 ~ 2.5 - - 1.7∙10 MeV/g* <( • (Green dashed vertical line on plot) 1ij 2.0 - - Cl) C) n, • ~ 1.5 - I - >0 • • 'E 1.0 - I •• I - •-•-•-•·•· / .I • • • ~ • • •-•-· ~ 0.5 - I - I I I 0.0 I 1010 1011 1012 Displacement Damage Dose [MeV/g] Modified from: Harris, IEEE REDW, 2007 *Europa Clipper DDD(Si) behind 100 mil Al From: JPL D-80302, Aug 18, 2016. To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 14 Silicon Carbide: WBG RHA WBG ~ CD Displacement Damage Dose Effects G) :::0 I • )> • SiC Schottky diodes are DDD-robust SiC SBD vs. JBS • Schottky barrier diodes (SBD) may be 102 ,...., ----· more tolerant than junction barrier N - I -- E 10° diodes (JBS) 0 I <( – Most commercial SiC Schottky’s are JBS ...... 10·2 ~ • Protects the Schottky barrier from the high field ti) C: 4 achievable with WBG materials (1) 10 C..., C: (1) 10-6 ... SBD pre ::::, •·-0-·· SBD post u 10-8 • -- JBS pre ODD= 1.9x1011 MeV/g - •- JBS post 1 o -1 0 -1 0 1 2 3 4 5 6 7 Forward Voltage [V] Luo, IEEE TNS, 2004 To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 15 Silicon Carbide: WBG RHA WBG ~ Displacement Damage Dose Effects 0) G) • :::0 I Si vs. SiC )> 3.0 I • SiC Schottky diodes are DDD-robust ,..... I * -•- SiC JBS (300V) • : -•-SiC JBS (1200V) • Schottky barrier diodes (SBD) may be ~ 2.5 1 I <( * -<>- Si SBD (150V) : / -A- Si SBD (60V) harder than junction barrier diodes (JBS) -1u 2.0 * - • - Si PIN (1600V) 1 • - 0 - Si PIN (1200V) • Direct comparison with Si is difficult & ;I O – Harris, 2007 showed carrier removal rate in SiC ~ 1.5 *• / / 0 I / ~ • Schottky diodes was higher than in Si Schottkys, > o •• I 'E 1.0 ;,....:::::...._1-----•--•-•-•-•·•• .,i suggesting Si more DDD tolerant ~ I • •-•-• 0 .... Ah-• • Comparison was of 4H-SiC JBS vs. Si SBD u. 0.5 l-----!----<'.~--~--0~ -v-v.., t----+---.c.•---.c.~---.c.-A-A-A·A-A – NSi Pi diodes were least DDD tolerant as expected I (minority-carrier device) 0.0 ---·=---~~~~------1 1010 1011 1012 • Higher-voltage rated devices were less tolerant Displacement Damage Dose [MeV/g] • At higher temperature, SiC removal rate may be Modified from: Harris, IEEE REDW, 2007 reduced (see Lebedev, Semiconductors, 2002) Are Si Schottky’s more DDD tolerant than SiC or is the difference due to device structure and voltage rating differences? To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 16 Silicon Carbide: Displacement Damage Dose Effects WBG RHA WBG ~ OJ G) • ::0 I )> • Impact of DDD is temperature dependent: – DDD effects in SiC reduced when measured at 300°C JFET Performance with Dose at 25 °C and 300 °C: • In agreement with Lebedev’s 2002 work suggesting 50 -.------...,.....~~-.-~~~~~-~...... --prerad reduced carrier removal rate at higher temperature - - - 2x1012 MeV/g •····· 2x1013 MeV/ 40 – Primary effect is donor compensation ---- < 300 °C ------....E • Impacts transconductance, pinch-off voltage, and ------c 30 ...Cl) on-state resistance ...::::, .. .. U 20 ···················· .... C: ..- -······· "§ .. • C ..···· 10 ....- ······ ..- ······ .... 0 ••· 0 +-~~~~~-~~-.-~~~~ ~-~...... -t 0 5 10 15 20 0 5 10 15 20 Drain Voltage M Drain Voltage M Modified from: McGarrity, IEEE TNS, 1992 SiC DDD tolerance increases with temperature, and SiC can operate at these high temperatures To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 17 Silicon Carbide: Displacement Damage Dose Effects WBG RHA WBG ~ • o::J G) 6H-SiC JFET vs. 4H-SiC JFET ::0 • SiC DDD tolerance depends on I )> 1.1 ....-----.-...... ,...,.,... _____,----,-...... ,..,...... ,-...... --...... ~ _..... ~ ~---~- ...... _...... _...... _..... ~...... a> 1 -IJ-4H-SiC 9m polytype Uc: I -4-6H-SiC g m I ____ m – Comparison of 4H- and 6H-SiC JFETs from ...., 1.0 ;t. - ~ Popelka (2014) and McGarrity (1992), t------c---lJ ~4 I respectively, suggests 6H-SiC more tolerant ~ 0.9 \ – Lebedev , JAP 2000, shows that defect behavior ~ IJ I- 0.8 differs between 4H- and 6H-SiC: "C -Cl)~ • Uncompensated donors increase with m radiation in 6H-SiC but decrease with 4H-SiC E... 0.1 z0 – McGarrity (1992) calculated a carrier removal rate 0.6-+-----.-...... ,...,.,...___.._,----,-...... ,..,...... ,-...... -- ...... ~---.- ...... -1 ~3x lower than Si, suggesting 109 1010 1011 1012 1013 6H-SiC more DDD tolerant than Si ~---Displacement Damage Dose [MeV/g] Modified from: McGarrity, IEEE TNS, 1992; and • Apparent discrepancy with Harris (2007) findings Popelka, IEEE TNS, 2014 regarding SiC vs. Si may be due to polytype Green dashed line: Europa Clipper DDD(Si) behind 100 mil Al From: JPL D-80302, Aug 18, 2016. For most missions, DDD in SiC will not be a concern. Actual DDD performance depends on device structure, polytype, and application temperature. To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 18 Silicon Carbide: Total Ionizing Dose Effects in MOSFETs WBG RHA WBG • ~ OJ Despite thick oxides, SiC MOSFETs can be TID- G) 0 Approx. ~ ::0 Cl) robust: I Orbit 1-year TID CJ -1 )> ..Ill [kradISi)] 0 > -2 'ti • 0 Cree Gens 1 & 2 in spec up to 100 krad(Si) Europa .c 300* 1/) -3 Clipper Cl) .c.. – Above 300 krad(Si), significant gate-drain capacitance I- -4 GEO 150 .!: changes can strongly impact switching performance Cl) CJ Polar LEO 5 C -5 .cIll u ISS LEO 1 -6 • Expect variability between manufacturers and 0 500 1000 1500 *100-mil Ta shielding per Total Ionizing Dose [krad(Si)] processes JPL D-80302, 8/18/2016 – Hole trapping depends strongly on NO anneal time o prerad a 300 krad(Si) and temperature 1::,. 600 krad(Si) .sLi:' – Interface state formation with radiation can vary Cl) c.> _eC 0.1 – Substantial fundamental differences between radiation ·u Ill Q. responses of Si and SiC MOSFETs found via Ill u electrically detected magnetic resonance (EDMR) CRSS 0.01 +---~--~--~-~--~-~ 0 10 20 30 40 50 Drain-Source Voltage [VJ TID hardness is coincidental and may change Plots modified from: Akturk, IEEE TNS, 2012 To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 19 Silicon Carbide Schottky Diodes: Single-Event Effects • WBG RHA WBG ~ I OJ I G) ·.x Region 3 I ::0 I I I )> F~- ·1· ------~::;:~ ~- -~"/-· ;------ ~ 5 I Q)U I ~ I I I I ------T--r--- 1 I I I ~ Q) Region 1 I I ..., Ol I I (.) .... Ql ca I I = .c I I uou I I NASA GRC: A. Woodworth, 2015 Bias Voltage [VJ Kuboyama, IEEE TNS, 2006 • SEEs in SiC Schottky diodes include: – Transient charge collection – Permanent increased leakage current – Catastrophic single-event burnout (SEB) Kuboyama, IEEE TNS, 2006 To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 20 Silicon Carbide Schottky Diodes: Single-Event Effects – Thresholds 3 • 10 ..------:----;------;----,---,--Fcs~ol;:ar:'."-:m~i~ni:m~um:::::===n Thresholds 102 -=-= ~"" ..:..:." :.:....:.~ =.:::.'v':.'..:....:..~ =-- ~~~~~~~:::l 100-mil Al shielding WBG RHA WBG 1200 ~~-:;:--:;;-~--.,_ =~~~~ ..... 101 ~ Cl) '>. 10° G) 1000 "C"' 10·1 "Iron Knee": N ::0 2 max LET(Si) = - ·e 10· 2 I 2:. aoo 29 MeV-cm /mg )> Q) ~ 10.J roen 600 ~ 104 :!:: u. 10.s g 400 ~ 10-6 Cl ,e 10·7 200 c: 10-a ~:::._- _----,-ln...,.te_rn_a-::-tio-na-;-l-;;;;Sp::--::a~ce::-;S:;::ta::;;tio::::::-n I- Polar 10·9 I 1 00 1 o -10 -F~ -==;::: ~ ~Ge~o~st~at;::::io9na=ry;::::::;=::::;:::=;:=a.=r~::::--"---:r:::----:~-=-::;:-' 0 10 20 30 40 50 60 70 80 90 100 Linear Energy Transfer (Si) [MeV-cm2/mg] Witulski, IEEE TNS, 2018 • 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 Typical risk-avoidant mission LET requirements for SEB are > 40 MeV-cm2/mg To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 21 Silicon Carbide Schottky Diodes: Single-Event Effects – SEB • Thresholds 10 1200 - Ion, Bias - Xe, 475V WBG RHA WBG Thresholds for SEB 1000 - Xe, 485V ~ 8 co have uncertainty: G) -> ~ 800 <( QJ 6 :::0 - ._..E at VR = 485 V, after I Ol 600 .... )> ro C 4 2 .:!::::! <10 Xe/cm , I = 10 mA 0 ...~ 4 R > 400 - u:::J with non-linearity of ∆IR 200 2 before that. Is this 00 fluence adequate to rule 00 50 100 150 200 Time (s) out SEB? (No) Witulski, IEEE TNS, 2018 Witulski, IEEE TNS, 2018 • 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 Adequate heavy-ion test fluence levels are difficult to obtain To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 22 Silicon Carbide Schottky Diodes: Single-Event Effects – Leakage current 1400 • -340 -7 .s~ 1200 i: -320 -8 .:r 2! E 1000 (.) WBG RHA WBG :i .9 () -300 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 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 To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 23 Silicon Carbide MOSFETs: Single-Event Effects • Increasing Drain-Source Voltage (VDS), with Gate-Source Voltage (VGS) = 0V 10·1 10·2 --Drain Current --- Gate Current 1.0x10"6 WBG RHA WBG 10-3 (abs. value) 10 MeV/u Xe ~ 104 10 MeV/u Xe -4 Flux = 6 cm·2s·1 co 5.ox10·1 G') ~ 10-S Flux = 20 cm·2s·1 ~ 2x10 0 VGS• 500 Vos ... 0 VGs• 600 V ... ::0 C 10-6 05 C ...QI I ... 10·7 ~ 0.0 - --- - ...... )> :I :I .. (J 10.a 4 .... u 1x10 -5.0x10·7 .... 10·9 10-10 10 MeV/u Xe ·1,ox10-6 Flux = 1500 cm·2s·1 10-11 ____ ,,,,,------· \, ------· 10-12 ..______...,... ______0 V Gs• 300 V05 o------1.5x10"6 +------.------...---... -20 -15 -10 -5 0 5 -20 0 20 40 60 80 100 -20 0 20 40 Elapsed Time [s] Elapsed Time [s] Elapsed Time [s] 10-s • Catastrophic failure or degradation shown in drain and a 0 ~ 10-6 a ... Spec/ gate currents (ID, IG) during 10 MeV/u Xe irradiation C ...QI 10-7 :I – Results shown are for a 1200-V device (J ~ 10.a Ill ~ 10 MeV/u Xe : 100 Vos Ill • At all biases above V = 50 V, part fails post-irradiation QI 10·9 Slope = 1.3x10·13 DS ...I QI CIC oOO ... Cl a 0 gate stress (PIGS) test 10-1 0 ~ Cl 0 10 MeV/u Ar: 300 V05 – At low V , PIGS outcome is dependent on ion fluence Slope= 2.6x10·15 DS 10-1 1-+---~~---~--~----...... f 102 103 104 105 SiC MOSFETs exhibit complex effects from heavy ions Fluence [cm-2] To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 24 SiC MOSFET Effects as a Function of VDS at VGS = 0 V: Latent Gate Damage • Grey = no ion effects; Green = VDS range for which only latent damage occurs 1500 (to 3300) WBG RHA WBG 1400 • No Effect Latent Gate Degradation ~ 10• I I _,, a 0 co 10• 1300 G) " 10J 1200 - - - - ::0 - - - 10• I -- -- )> 10 MeWu Xe: 100 V05 s;-1100 10• S!ope • 13x10'11 a" oOO a" 0 t--- 10•ID -OJ 1000 a 0 10 MeV/u At: 300 VD! tl.O Slopes:26x 10'tS 10'H ro -- -- +-' 900 10' 10' 10• 10• 10• --- 0 Ftu ence (cm4) > 800 Q) u - Source Voltage lo.. 700 :, 0 600 ------Q Collection I ↑ V') GSS I C 500 ------• ro lo.. Drain No Measurable ------0 400 - Q Collection t--- Effect 300 t--- - - During Irradiation Post Run 200 ------100 ------0 - Measurement Results Device: Ml M2 M7 Ml M2 M3 M4 MS M2 M3 M4 MG M7 MS Ion/LET: B 0.9 Ar 8.9 Arl0 Cu 23 Ag47 Xe 63 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 To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 25 SiC MOSFET Effects as a Function of VDS at VGS = 0 V: Latent Gate Damage • Grey = no ion effects; Green = VDS range for which only latent damage occurs 1500 ~ ------(to 3300) 1400 • No Effect Latent Gate Degradation 10• WBG RHA WBG _,, a 0 10• 1300 ~ " co 10J G') 1200 10• ::0 10 MeWu Xe: 100 V05 s;-1100 I 10• S!ope• 13x10'11 a" oOO )> 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) g Q) u - Source Voltage lo.. :, 0 Q Collection I ↑ V') GSS I C ------• ro lo.. Drain No Measurable Q Collection 0 Effect During Irradiation Post Run 100 0 Measurement Results Device: Ml M2 M7 Ml M2 M3 M4 MS M2 M3 M4 M6 M7 M8 Ion/LET: B 0.9 Ar 8.9 Arl0 Cu 23 Ag47 Xe 63 No latent damage to gate from low LET/light ions To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 26 SiC MOSFET Effects as a Function of VDS at VGS = 0 V: Latent Gate Damage • Grey = no ion effects; Green = VDS range for which only latent damage occurs 1500 ~ ------(to 3300) 1400 • No Effect Latent Gate Degradation 10• _,, a 0 10• 1300 WBG RHA WBG " ~ 10J 1200 co G) 10• 10 MeWu Xe: 100 V05 s;-1100 10• S!ope• 13x10'11 ::0 a" oOO a" 0 I 10•ID -OJ 1000 a 0 10 MeV/u At: 300 VD! tl.O )> Slopes:26x 10'tS 10'H 900 10' 10' 10• 10• 10• 2 Ftuence (cm4) g 800 Q) - Source Voltage ~ 700 :, o 600 Q Collection I ↑ V') GSS I ------• C 500 ,_ro Drain No Measurable Q Collection o 400 Effect 300 During Irradiation Post Run 200 100 0 Measurement Results Device: Ml M2 M7 Ml Ion/LET: B 0.9 Ar 8.9 Arl0 Onset is independent of MOSFET voltage rating and manufacturer/generation at higher LETs To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 27 MOSFET Effects as a Function of VDS at VGS = 0 V: Degradation During Beam Run • Yellow = VDS range for ∆ID = ∆IG degradation Green = VDS range for which only latent damage occurs ·1·,···0X1·0·~. 1500 (to 3300) 5.0x10 -1 ··•"--- ~ 1400 I • No Effect Latent Gate Degradation D ld=lg I ...... 1300 -1 .0xt O,. :~~~~ecn,·~ ·• WBG RHA WBG 1200 ------0 Vos, 300 Vos ~ -t.Sxt o• +---~-~---- co -20 0 20 •• s;1100 -- -- G') E13psed Time [s) -OJ 1000 - ::0 tl.O I ↑ I I , I ↑; ...... ro 900 ------)> DG GSS DSS i 0 Color gradients > 800 ∆ID = ∆IG Failed I Q) span between GSS u - Source Voltage ------• .... 700 :::, known VDS 0 600 ------Q Collection IGSS ↑ V) I for given C 500 ------• ro response types Drain .... No Measurable ------0 400 f---- Q Collection - f---- Effect 300 - - - - - 200 -- -- - During Irradiation Post Run - - 100 ------f------0 Measurement Results Device: Ml M2 M7 Ml @ M3 M4 MS M2 M3 M4 MG M7® Ion/LET: B 0.9 Ar 8.9 Ar 10 Cu 23 Ag47 Xe 63 Not all MOSFETs exhibit drain-gate leakage current degradation: Design techniques may eliminate this vulnerability To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 28 MOSFET Effects as a Function of VDS at VGS = 0 V: Degradation During Beam Run :S.0ll 10""' - 10 2.lb:10" ••••la • SOOVir,5 2..0:1:10"' ~ Mev:xe Ave. Flux: 6 cm4 1-·1 Blue = V range for ∆I >> ∆I degradation 1.&:-10 ... DS D G 1.0 :ic 10... Yellow = VDS range for ∆ID = ∆IG degradation ~ ------(to 3300) 0.0 1500 ... .. 100 Elap$ed Time (•) 1400 • No Effect La t ent Gat e Degradation • ld=lg • ld>lg 1300 I ↑; ↑i IDG, IDS DSS i 1200 WBG RHA WBG s;1100 ~ ∆ID >> ∆IG ↑ or Failed IGSS co ------• -OJ 1000 G) tl.O ::0 ↑ IDG IGSS , IDSS ↑; .g! 900 I i i Color gradients )> g 800 ∆ID = ∆IG Failed I Q) span between GSS u - Source Voltage ------• .... 700 :::, known VDS 0 600 Q Collection IGSS ↑ V) I for given C 500 ------• ro response types Drain No Measurable .... Q Collection 0 400 Effect 300 During Irradiation Post Run 200 100 0 Measurement Results Device: M l M 2 M 7 M l M 2 M 3 M4 MS M2 M3 M4 M G M7 MS Ion/LET: B 0.9 Ar 8.9 Arl0 Cu 23 Ag47 Xe 63 IDS degradation least influenced by electric field and ion LET: linked to material properties?? To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 29 MOSFET Effects as a Function of VDS at VGS = 0 V: SEB/GR Red = V range for SEB/GR • DS Blue = VDS range for ∆ID >> ∆IG degradation Yellow = VDS range for ∆ID = ∆IG degradation Sudden Catastrophic Failure: 1500 ~ ------(to 3300) high-I event BVDSS < 2 V 1400 D No Effect Latent Gate Degradation D ld=lg • ld>lg • SEE 1300 ------•I ↑; ↑i IDG, IDS DSS i 1200 ∆I >> ∆I ↑ or Failed I s;1100 WBG RHA WBG D G GSS ------• -OJ 1000 tl.O ↑ I I , I ↑; ,g! 900 i DG GSS DSS i Color gradients g 800 ∆ID = ∆IG Failed I Q) span between GSS u - Source Voltage ------• .... 700 :::, known VDS 0 600 Q Collection IGSS ↑ V) I for given C 500 SEB/GR onset not found ------• ro response types Drain No Measurable .... Q Collection 0 400 Effect 300 During Irradiation Post Run 200 100 0 Measurement Results Device: Ml M2 M7 Ml M2 M3 M4 MS M2 M3 M4 MG M7 MS Ion/LET: B 0.9 Ar 8.9 Arl0 Cu 23 Ag47 Xe 63 SEB/GR vulnerability at LET(Si) < 1 MeV-cm2/mg Vulnerability saturates before the GCR flux “iron knee” To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 30 SiC Radiation Hardness by Process: 1200 V MOSFET • 1500 1400 D No Effect • Latent Gate Degradation • ld=lg • ld>lg • SEE 1300 • Reduced SEB/GR susceptibility 1200 ~1100 – Thicker epilayer Q) 1000 tl.0ro +-' 900 g 800 Q) ,._u WBG RHA WBG 700 =, ~ 0 co V) 600 G) I C 500 :::0 ,._ro I Cl 400 )> Color gradients 300 span between 200 100 known VDS for given 0 Device: Baseline Modified response types Ion/LET: Ag47 After Zhu, X., et al., 2017 ICSCRM Just as with silicon MOSFETs, epilayer optimization must be done to balance SEE tolerance with on-state resistance (RDS_ON) performance To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 31 SiC Radiation Hardness by Process: 1200 V MOSFET • 1500 1400 D No Effect • Latent Gate Degradation • ld=lg • ld>lg • SEE 1300 • Reduced SEB/GR susceptibility 1200 ~1100 – Thicker epilayer Q) 1000 tl.0ro +-' 900 • Degradation of IDG eliminated g 800 Q) ,._u 700 – Drain neck width reduction =, WBG RHA WBG 0 V) 600 ~ I OJ C 500 G) ,._ro ::0 Cl 400 I )> Color gradients 300 span between 200 100 known VDS for given 0 Device: Baseline Modified response types Ion/LET: Ag47 After Zhu, X., et al., 2017 ICSCRM Elimination of drain-gate leakage current degradation mode is possible through established silicon MOSFET hardening techniques To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 32 SiC Radiation Hardness by Process: 1200 V MOSFET • 1500 1400 D No Effect • Latent Gate Degradation • ld=lg • ld>lg • SEE 1300 • Reduced SEB/GR susceptibility 1200 ~1100 – Thicker epilayer Q) 1000 tl.0ro +-' 900 • Degradation of IDG eliminated g 800 Q) ,._u 700 – Drain neck width reduction =, 0 V) 600 WBG RHA WBG I ~ C 500 • Minimal change in onset of Cl) ,._ro G) Cl 400 other degradation effects: ::0 300 I Color gradients )> 200 span between .....,_._._..,.,,.. ...,_-_ -_ -_ -_ -_ -_ -_ -_ -_ .....---1 – ∆ID >> ∆IG 100 known VDS ~======1 • for given 0 – latent gate damage Device: Baseline Modified response types Ion/LET: Ag47 • Rate of degradation at a given After Zhu, X., et al., 2017 ICSCRM voltage is reduced Continued research and development efforts are necessary to understand residual degradation mechanisms! To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 33 Normalized Onset Voltage for Immediate SEB/GR: Comparison of Device Types • 1.0 0.9 SEB/GR: 'ff MOSFET 0.8 0 Schottky Diode Q) • JFET 0.7 g> ~ PIN Diode ~ 0 > 0.6 "C Q) 0.5 .!::! n, 0.4 E I '- WBG RHA WBG 0 0.3 ~ z co 0.2 G) i :;o 0.1 I • 0.0 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 Linear Energy Transfer (Si) [MeV-cm2/mg] 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 34 Comparison of SEB/GR Susceptibility Across SiC Power Devices: Neutron Data • Terrestrial neutron failures-in-time (FIT) data normalized to the active die area, as a function of bias voltage normalized to measured avalanche voltage. Sea-level Neutron FIT/cm 2 . . X 10000 ...... ; ...... ; ...... ,...... (1) :X 1000 ~ 103 ,,,,,,,...... ,,,,!••········· ········••:-••••· ················· cu • .... , (1) • ,, ... . Cl) . , , . 2 N 100 IA\ 10 ,., .. . , ... , ...... j, ..~ ...,t,,, .•'. . .. . ; ...... , E v:::!I . , • u N WBG RHA WBG !.a.. • : 1 10 ~ ...... • Wolfspeed 1700 t:: OJ 5 10 t F, ...... LL G) ~ ,,.. .a. !. X STMicro 1200V ::0 u. 0 w O Rohm 1200V I 1 o ...... ; ...... • Microsemi 1 )> . .a. Wolfspeed 1700 0.4 0.6 0.8 1 0.1 BiasN (VN) ava 1 0.3 0 .4 0.5 0.6 0. 7 0.8 0.9 1.0 1.1 Vo/ Vava l Used with permission from: CoolCAD Electronics (left), Wolfspeed (right) 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. To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 35 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 WBG RHA WBG ~ • For risk-tolerant applications, margin and unpowered redundancy is advised c:o G) :::0 – Life tests of damaged parts may reveal higher-likelihood failure modes - sample size will limit I )> discovery of rarer modes • Remember to consider other non-RHA concerns: – There are no space qualification standards specific for WBG technologies ObscrT=· cd Failun: C:ilr'Out Failures Const.int (Ran d om) ..·· Failures ••••• . I I ····•• Jt • •••• • •••••••••••••• ••••• •••( ••••• ••••••••••••• Time To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 36 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 V WBG RHA WBG requirements ~ OJ C) – LET should be specified in terms of LET(Si) but penetration range must be for SiC :;o I )> • Characterization data should include identification of voltage conditions at which I different effects occur – Richer dataset will include how susceptibility to these effects changes with ion species/LET/angle/temperature To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 37 • /' WBG RHA WBG ~ OJ G) ::0 I )> I GALLIUM NITRIDE HIGH ELECTRON MOBILITY TRANSISTOR (HEMT) RADIATION EFFECTS To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 38 GaN HEMT Outline • • Introduction to GaN high electron SEE failure sites (ex/ right photo) superimposed onto mobility transistors (HEMTs) optical image (left) suggest random distribution • Effects of radiation: – Displacement damage dose – Total ionizing dose – Single-event effects • RFN Ga HEMTs • Enhancement-mode HEMTs V WBG RHA WBG • Radiation hardness assurance ~ CD G) guidance :::0 I Images: NASA JPL, courtesy of L. Scheick )> To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 39 GaN HEMT Introduction: Device Structure • Two primary flavors of GaN HEMTs: • – Depletion mode (normally on) – Enhancement mode (normally off) Source Gate Drain AlGaN Barrier • Normally-off GaN is achieved in several ways: GaN – Cascode with a low-voltage normally-off silicon AlGaN Buffer MOSFET AlN (seed layer) • Penalty to RDS_ON lessens with higher voltage-rated GaN HEMTs Substrate (SiC, Si, …) – p- doped GaN gate • Used in first commercial eGaN devices Typical GaN HEMT structure sets up lattice strain • Gate built-in voltage exceeds piezoelectric field and charge polarization between the AlGaN – Recessed Schottky gate barrier and GaN layer, creating a 2-dimensional path for electrons to flow WBG RHA WBG • Thinned AlGaN barrier beneath gate to reduce piezoelectric voltage below Schottky built-in voltage E – Flourine- implanted AlGaN barrier C EF • Traps negative charge in the layer EV Metal Gate AlGaN GaN Many gate designs: How will these differences affect Energy band diagram showing space qualification standards development for GaN? 2-D electron gas formation (yellow) To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 40 GaN HEMT Introduction: Applications • RF GaN HEMTs • – Initially, RF applications dominated due in part Output Signal to depletion-mode operation – Designed to work well in linear region for max gain, min distortion • Characterization includes incident and reflected wave Input Signal power measurements as well Gate-Source Voltage M • Enhancement mode GaN HEMTs as switches RF apps often operate in linear region – Development of normally-off HEMTs provided in-road to power management applications ::f. • Start-up does not require an initial gate bias to be applied c ~ to avoid short-circuit damage :::, v (.) C: WBG RHA WBG -~ ~ – Designed to work well in on-state/transition OJ 0 G) states to minimize losses ::0 I )> • Low RDS_ON and off-state drain leakage current (IDSS) Drain-Source Voltage [VJ Switch apps operate along load line Can a single set of radiation test method standards be developed for both RF GaN and enhancement-mode GaN HEMTs? To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 41 GaN HEMTs: Displacement Damage Dose Effects • GaN HEMTs out-perform GaAs HEMTs • Parametric degradation in GaN HEMTs 1.0 !• I "' .., t· Current occurs at DDD levels far above those for c ••• ~t i a J f Da7 ~ 0.8 ... ::, . space applications () • * "' ~.· C • ' "' * t :] -~ 0.6 – Weaver, et al., 2015 show order-of-magnitude 0 ... * • a1 • N X"' better performance of GaN vs. GaAs HEMTs ~ 0.4 X • E 0 ...... •. z GaAs • GaN – Possibly due to re-injection of 0.2 scattered carriers 1E9 1E10 1E11 1E12 1E13 Displacement Damage Dose (MeV/g) • GaN HEMT DDD effects include Weaver et al. ECS J. Solid State Sci. Technol. 2016. Used with permission. – Decreased drain current Power gain decreases despite correction of ∆ID 13~------~ – Threshold voltage shift (typically positive) ✓ 12.5 WBG RHA WBG – Decreased mobility and transconductance ~ Cl) 12 C) iii' 11 .5 – Decreased power gain ::0 :!:!. I c: 11 ·;;; • C> 10.5 • Pre • 3x1012 10 1x1013 For extreme DDD environments, use of a feedback 13 9.5 .. 3x10 • 1x1014 1.8 MeV protons system to maintain quiescent ID will improve ?is -20 -1s -10 -s o s 10 15 Input Power [dBm] radiation tolerance Ives, IEEE TNS 2015. Used with permission. To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 42 GaN HEMTs: Displacement Damage Dose Effects • Concentrations of existing defects increase • DDD susceptibility is greater when: with radiation exposure – parts are biased during irradiation n-GaN:Si p-GaN:Mg – parts have had prior hot-carrier stress ~-0.13ev, +3.28eV E -0.16eV-. Ec-0.60eV ----Ev+3.00eV – see Chen, et al., IEEE TNS 2015 E -0.71eV Ey+2.42eV • Radiation increases the concentration of ---- - Ev+1 .50eV as-grown traps existing defects irradiation-induced traps E -3.25eV ~===~~---- EF VB Pearton, ECS J. Solid State Sci. Technol. 2016. Used with permission. /' WBG RHA WBG ~ OJ G') GaN HEMT DDD effects: ::0 I )> 1) Bias matters during irradiation 2) Prior hot-carrier stress can enhance radiation effects 3) There is significant variability of response to radiation To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 43 GaN HEMTs: Total Ionizing Dose • GaN HEMT designs vary • 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 1 µm >-< EHT=1000kV Signal A ., SESI Date .28 Apr 2016 WD : 70mm Mag= t0OOKX FIB Loc:t< Mag$ ., No – 500 krad(Si) γ irradiation: < 18% Vth shift (Lidow, 2011) • MOS gate V – No data WBG RHA WBG ~ OJ – This design is most likely to be sensitive to TID G) ::0 effects I )> GaN HEMT TID effects: EHT • 10.00 kV Signal A • SESl o.te.2GA9{2018 WO• 71mm Mag • 3.15KX F18 Lode Mags ,. No 111 Robust in absence of gate oxide; Images: NASA JPL To be determined for those with oxides To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 44 RF GaN HEMTs: Single-Event Effects • • 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 / WBG RHA WBG ~ OJ G) :::c I )> Although generally SEB-robust, some unpublished SEB failures have occurred at biases relevant to RF operation To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 45 RF GaN HEMTs: Single-Event Effects • • 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 lx l0-3 ------1 8x l04 L.;14*015 ~ V ~ i: IDrain Current I JI ~ ~ 6x l04 u 130 ID and IG as a function of ~ 90 120 ~i'3 4xJ0-4 3.5 MeV/u Kr fluence and VDS ....J 11 0 reveals 2 damage pathways 100 )t:,;jent I / 2x l04 WBG RHA WBG ~ OJ 30 40 50 G) 0 5xl07 lx l08 l.5x I os :::0 I Fluence [cm-2] ):> Kuboyama, 2011 IEEE TNS. Used with permission. All heavy-ion studies of RF GaN HEMTs report increased leakage current To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 46 Enhancement-Mode GaN HEMTs: Single-Event Effects • • 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 Variable effect of angle on – Angle effects are variable SEB susceptibility @ g • Variability between lots of same part (Scheick, 2018) 800 • Compounds difficulty of estimating an on-orbit failure rate 600 • Increased leakage currents: 400 – Drain-source leakage current affected 200 WBG RHA WBG ~ 0 OJ Drain-to-Source (Vds) [V] G) 0 20 40 60 Angle [Deg] ::0 I NASA, courtesy L. Scheick. )> Lot-specific testing is critical To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 47 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 WBG RHA WBG ~ OJ – Current collapse G) ::0 I – Dynamic RDS_on )> – And others To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 48 The Future • A GLIMPSE INTO THE FUTURE To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 49 Qualification Standardization & Technology Maturation • • Supplier qualification data are based on standards for silicon The Future – 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 To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 50 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 The Future • 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 Creative Commons CC0 To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 51 Ultra WBG: Diamond • Benefits: • – Best of everything (see plot) – High electron and hole mobilities – Electron emissivity Bandgap Energy ~ - [eV] ~ ~~k ~~- 0/4 C' --~ • Target applications: “Ultra-high power” market (1 kW <$>~. ~$ 0~ ,S' or more) ,' Electron ,' – Radar Saturation Velocity Electric Field [x107 emfs] [MV/cm] – Communication satellites \ Fast Switching \ ,' - Si – Vacuum electronics (driver, cathode) \ Applications --4H-SiC '\ \ --GaN • Status: \ --c \ \ – 10 mm x 10 mm wafers commercially available Melting Point Thermal Conductivity The Future – Vertical SBDs, MESFETs, and MOSFETs have been [x1000 °C] [W/cm/°C] developed High Temperature Applications • Challenges for maturation – Crystal quality and size – Absence of n-doping To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 52 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 Bandgap Energy ~ - [eV] ~ ~~k ~~- 0/4 – Wafer costs are comparable to GaN C' --~ <$>~. ~$ 0~ • Target applications: “Ultra-high power” market (1 kW ,S' Electron or more) Saturation Velocity Electric Field 7 [MV/cm] – Radar [x10 emfs] Fast Switching – Communication satellites - Si Applications --4H-SiC – LED market --GaN --f3-Ga20 3 • Status: – Least mature of the ultra-WBG technologies Melting Point Thermal Conductivity [x1000 °C] [W/cm/°C] – 2” Wafers commercially available High Temperature Applications – Vertical SBDs, MESFETs, and MOSFETs have been developed • Challenges for maturation – Crystal quality The Future – Absence of p-doping; self-trapping of holes – High contact resistance – Thermal management: poor heat dissipation To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 53 • Thank you for your attention! To be presented by J.-M. Lauenstein at the Radiation Effects on Components and Systems (RADECS) Topical Day, Gothenburg, Sweden, September 16, 2018 54