GaN MMIC PAs for MMW Applicaitons Miroslav Micovic HRL Laboratories LLC, 3011 Malibu Canyon Road, Malibu, CA 90265, U. S. A. mmicovic@hrl.com © 2008 HRL Laboratories, LLC. All Rights Reserved Motivation for High Frequency Power sources 60 GHz – 110 GHz Frequency Spectrum High Data Rate Wireless Links (10 Gbits/s) Commercial Bands (E-band radio) 71 GHz – 76 GHz, 81 GHz – 86 GHz, 92 GHz – 95 GHz Inter-Satellite 59.3 GHz – 64 GHz Active Millimeter-Wave Imaging 94 GHz SAR, Phase Array Radar (Space based W-band radar for earth studies.) RF Sources for THz Multiplier Diodes Fundamental Power for THz Space Array Spectroscopy Power Required ≈ Watts Available Sources < 200 mW GaN MMIC ≈ 3 W at 95 GHz © 2008 HRL Laboratories, LLC. All Rights Reserved Microwave and Millimeter-wave Solid State Sources 1000 Pulsed mode Estimated CW GaN limit Pout [W] 100 Estimated CW LDMOS limit 10 Estimated CW GaAs limit HRL GaN 2008 Symbols: LDMOS catalog items GaAs catalog items GaN reported data 1 HRL GaN 2007 HRL GaN 2006 0.1 0.1 1 10 Frequency [GHz] Output power per single die. © 2008 HRL Laboratories, LLC. All Rights Reserved 100 HRL W-band GaN Roadmap Extrapolate Extrapolate>3 >3W! W! Output Power (mW) 3,500 3,000 Q3 Q32008 2008 Plan Plan 2,500 2006 2006HRL HRL IEDM IEDMpaper paper 2,000 1,500 1,000 HRL HRLIR&D IR&D 2007 2007 500 Q4 Q42008 2008 Plan Plan 0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 Best BestGaAs GaAs pHEMT pHEMT and 1.8 andInP InPHEMT HEMT Gate Width (mm) DisruptiveW-band W-bandGaN GaNPower PowerMMICs MMICs Disruptive 8Xhigher higherpower powerdensity densitythan thanmmW mmWGaAs GaAspHEMT pHEMT 8X © 2008 HRL Laboratories, LLC. All Rights Reserved Cost trade-off estimate for 3 Watt W-band SSPA GaAs pHEMT SSPA GaN SSPA 8-way waveguide combining 8-way splitter and 8 way combiner required Power combining not required Number of WR-10 power modules 8 1 Number of MMIC’s per module 3 (Attenuator, Phase Shifter, Power Amplifier) 1 (Power Amplifier only) Hand-tuning to obtain phase and amplitude match for combining Combiner arms tuned manually No tuning Watt95 95GHz GHzGaN GaNSSPA SSPAisisCost CostEffective Effective 33Watt © 2008 HRL Laboratories, LLC. All Rights Reserved W-band GaN MMIC Device T-gate device Passivation Lg = 0.12 µm Low ohmic contact resistance < 0.2 Ω/mm. Gate Source Ohmic n+GaN Comparable to GaAs pHEMT’s and InP HEMT’s. Drain Ohmic n+GaN Smooth ohmic metal edges. Recessed gate Bi-layer e-beam gate litho AlGaN Schottky barrier Lg = 0.12 µm for Ka-band GaN SiN passivation and capacitor dielectric AlGaN buffer 2 µm Source-Drain separation SiC substrate TaN 50 Ω/Square resistor Epi resistors N+ layer facilitates fabrication of ohmic contacts. Double Heterojunction Structure © 2008 HRL Laboratories, LLC. All Rights Reserved Short Channel Effects - Buffer Isolation 10 Ef 0 -1 18 16 10 Al Ga 0.26 N 0.74 GaN 14 10 -2 12 10 -4 10 0 200 400 600 800 Position [Angstroms] 10 1000 Ec 1 18 10 Ef 0 1016 -1 Al0.3Ga0.7N GaN Al Ga 0.04 14 10 -2 12 10 -3 Ev -4 10 0 200 400 600 800 Position [Angstroms] Techniques used to improve backside confinement and buffer isolation Doping – Fe doped buffer layer; Y.-F. Wu et al., El. Dev. Lett., Vol. 25, pp 117-119 – C doped buffer layer; S. Rajan et al., El. Dev. Lett., Vol. 25, pp 247-249 Polarization Engineering – GaN DHFET structure; M. Micovic et al., IEDM 2004 Digest, pp 807-810 – InGaN back barrier; T. Palacios et al., El. Dev. Lett., Vol. 27, pp 13-15 © 2008 HRL Laboratories, LLC. All Rights Reserved N 0.96 -3 -3 Ev -3 Electrostatic Potential [eV] 1 Electron Concentration [cm ] Ec 10 20 10 Electron Concentration [cm ] 2 DHFET 2 20 Electrostatic Potential [eV] Conventional SHFETHEMT 10 1000 Short Channel Effects - Buffer Isolation Transfercurves curves ofof GaN (blue) SHFET (red); Transfer LgDHFET = 0.12 µmand GaN HEMTs Both wafers have field plate gate structure; Vds=10V Conventional (Red), DHFET (Blue) 10000 1000 Ids [mA/mm] 100 Vds=10V 10 >1000x Leakage Reduction 1 0.1 Ids DHFET Idss SHFET 0.01 0.001 -5 -4 -3 -2 -1 Vg [V] DHFET Structure: -Improved Back-Channel Confinement, -Reduced sub-threshold drain leakage current. © 2008 HRL Laboratories, LLC. All Rights Reserved 0 1 2 Uniformity Better than 1% over 3” Wafer Epi Thickness 0.90 % AlGaN % 0.68 % Uniformity = Std. Dev. / Mean No edge exclusion © 2008 HRL Laboratories, LLC. All Rights Reserved Sheet resistance 0.46 % Individual Source Vias • 30x30 vertical wall vias in 50 µm substrate • Enables microstrip MMICs • Low source inductance < 10 pH – Critical for high power W-band power amp performance © 2008 HRL Laboratories, LLC. All Rights Reserved DC Device Characteristics Lg = 0.1 µm, Wg = 4 x 37.5 µm GaN HFET Vgs = 0 to -4 V 500 Ids gm 900 Step = -0.5 V 100 80 60 800 -1.0 V 700 350 -1.5 V 600 300 500 250 400 200 -2.5 V 300 150 -3.0 V 200 100 100 50 -2.0 V 40 20 0 0 2 4 6 8 Vds [V] 10 450 -0.5 V Ids [mA/mm] 120 Id [mA] 1000 Vgs =0 12 14 0 -4.5 400 0 -4 -3.5 -3 -2.5 -2 -1.5 Vgs [V] Idss = 900 mA/mm © 2008 HRL Laboratories, LLC. All Rights Reserved gm of 360 mS/ mm at Vds = 12 V -1 -0.5 0 gm [mS/mm] 140 Small Signal RF Performance 35 fT 30 MSG H21 Gain [dB] 25 = 90 GHz fmax = 200 GHz 20 15 10 5 0 1 10 100 Frequency [GHz] Lg = 0.1 µm, Wg = 4 x 37.5 µm GaN HFET Vds = 10 V, Ids = 45 mA. © 2008 HRL Laboratories, LLC. All Rights Reserved 500 mW 70 GHz GaN MMIC PA 70 GHz MMIC Chip Layout Size 3.4 mm x 1.3 mm Operating Voltage = 15 V Measured Gain > 15 dB Small Signal Gain, Return Loss [dB] 20 12 GHz Measured Bandwidth, Gain >response 15 dB,ofGain Ripple 0.5 dB frequency 70 GHz GaN<PA 82.3 GHz 16.16 dB 70.04 GHz 15.46 dB 10 71.02 GHz 15.42 dB 76.13 GHz 16.29 dB 0 -10 -20 60 70 80 90 Frequency (GHz) Measured small signal gain of 70 GHz 500 mW GaN MMIC PA. Performancemeets meetsdesign designgoal. goal. Performance © 2008 HRL Laboratories, LLC. All Rights Reserved Output power of 70 GHz MMIC measured at a frequency of 76 GHz Pout (dBm), Gain (dB), PAE (%) 30 Pout (dBm) Gain (dB) PAE (%) 25 20 15 10 Psat = 500 mW PAE = 17% P1dB = 24 dBm Vds = 15 V 5 0 0 1 2 3 4 5 6 7 8 Pin (dBm) © 2008 HRL Laboratories, LLC. All Rights Reserved 9 10 11 12 13 14 15 Comparison of 70 GHZ MMIC Performance with the best commercial pHEMT Parameter 70 GHz GaN MMIC PA Commercial GaAs pHEMT Gain >14 dB > 5 dB P1dB 24 dBm 20 dBm Psat 27 dBm 22 dBm PAE 16.5 % Input return loss < -8 dB < -4 dB Output return loss < - 8 dB < -2 dB Themost mostpowerful powerfulMMIC MMICreported reportedto todate dateat at70 70GHz GHz The © 2008 HRL Laboratories, LLC. All Rights Reserved 500 mW 80 GHz GaN MMIC PA 15 GHzfrequency Bandwidth, Gain > 11 dBGaN PA Measured response of 80 GHz 80 GHz MMIC Chip Layout Size 3.4 mm x 1.3 mm Operating Voltage = 15 V Measured Gain > 11 dB Small Signal Gain, Return Loss [dB] 20 10 76.37 GHz 14.97 dB 82.721 GHz 14.5 dB 86.062 GHz 12.07 dB 0 -10 -20 60 70 80 Frequency (GHz) 90 100 Measured small signal gain of 80 GHz 500 mW GaN MMIC PA. MMICDesigned Designedfor forE-band E-bandRadio RadioBand Band MMIC © 2008 HRL Laboratories, LLC. All Rights Reserved Output power of 80 GHz MMIC measured at a frequency of 83 GHz Pout , Gain, PAE [dBm, dB, %] 30 27 dB m P out G a in PAE 25 20 17 % 15 12 dB 10 Psat = 500 mW PAE = 17% P1dB = 24 dBm Vds = 15 V 5 0 -1 0 -5 0 5 10 15 Power modules using 2006 GaN SR parts used as a power source. 20 P in [d B m ] HighestOutput OutputPower Powerand andEfficiency Efficiencyreported reported Highest foraasolid solidstate statesource sourceat atthis thisfrequency. frequency. for © 2008 HRL Laboratories, LLC. All Rights Reserved Comparison of 80 GHZ MMIC Performance with the best commercial pHEMT Parameter 80 GHz GaN MMIC PA Commercial GaAs pHEMT Gain >11 dB > 5 dB P1dB 24 dBm 20 dBm Psat 27 dBm 22 dBm PAE 17 % Input return loss < -7 dB < -4 dB Output return loss < - 7dB < -2 dB Themost mostpowerful powerfulMMIC MMICreported reportedto todate dateat at80 80GHz GHz The © 2008 HRL Laboratories, LLC. All Rights Reserved 500 mW 90 GHz GaN MMIC PA Flat Response over 92 GHz- 95 GHz frequency band. 9 GHz Bandwidth, < -10 dBPA Measured frequency Return response Loss of 95 GHz GaN 90 GHz MMIC Chip Layout Size 2.4 mm x 1.3 mm Operating Voltage = 15 V Measured Gain > 15 dB Small Signal Gain, Return Loss [dB] 20 90.884 GHz 14.88 dB 10 88.865 GHz 14.52 dB 97.451 GHz 14.22 dB 0 -10 -20 80 90 100 110 Frequency (GHz) Measured small signal gain of 90 GHz 500 mW GaN MMIC PA. Performance Meets Design Goals © 2008 HRL Laboratories, LLC. All Rights Reserved Output Power of 90 GHz GaN MMIC measured at a frequency of 94.75 GHz Pout , Gain, PAE [dBm, dB, %] 25 23 d B m P o u t [d B m ] G a in [ d B ] P A E [% ] 20 15 1 3 .8 d B 10 P0.5dB = 23 dBm Linear Gain = 14.4 dB 9 % 5 0 -2 0 2 4 6 8 10 P in [d B m ] Output power limited by available input drive, circuit less than 0.5 dB compressed. HRL is building a power source using GaN MMIC to test the power. © 2008 HRL Laboratories, LLC. All Rights Reserved Comparison of 90 GHZ MMIC Performance with best commercial GaAs pHEMT Parameter HRL 90 GHz GaN MMIC PA GaAs pHEMT Gain >14 dB > 10 dB Gain Ripple < 0.5 dB < 1 dB P1dB >23 dBm 20 dBm Psat To be measured 23 dBm PAE To be measured Input return loss < -10 dB < -8 dB Output return loss < - 10dB < -8 dB © 2008 HRL Laboratories, LLC. All Rights Reserved 250 mW 100 GHz GaN MMIC PA Measured frequency response of 100 GHz GaN PA 100 GHz MMIC Chip Layout Size 2.4 mm x 1.3 mm Operating Voltage = 15 V Measured Gain > 15 dB Small Signal Gain, Return Loss [dB] 20 10 102.13 GHz 15.23 dB 95.912 GHz 15.19 dB 100.03 GHz 15.72 dB 0 -10 -20 80 90 100 110 Frequency (GHz) Measured performance of the first 100 GHz GaN MMIC chip. FastestGaN GaNMMIC MMICCircuit Circuit Fastest NearTerm TermPotential Potentialfor for150 150GHz GHz––220 220GHz GHz Near © 2008 HRL Laboratories, LLC. All Rights Reserved Summary • GaN MMIC technology will dominate high frequency > 50 GHz solid state RF power technology. • Key challenges for MMW GaN: – – – Ohmic Contacts Short gate lengths Device Structure • GaN MMICs exceeding power of best GaAs and InP MMICs at 95 GHz demonstrated. • GaN MMICs with 5 x power of the best InP MMICs are on the road map for 2009. MMW GaN MMIC technology enables new systems, applications and services. © 2008 HRL Laboratories, LLC. All Rights Reserved