ECE 695 Discussion Session GaN HEMT Technology – Recent Advances Yen-Sung Chen Feb. 15th 2017

Outline Material Properties Results from some groups MIT Purdue UND UCSB Fujitsu Panasonic HRL Summary

Comparison of Semiconductors for Power Devices Left: M. Yoder, TED, 1996 Right up: J. Hudgins et al., IEEE Transactions on Power Electronics, 2003 Right bottom: Y. Zhang et al., TED, 2016

MIT – GaN Nanoribbon HEMT 1. Al2O3/AlGaN interface fixed positive charge. 2. Al2O3 passivation layer induces biaxial tensile stress piezoelectric field in AlGaN layer increases. 2DEG density increases Sheet resistance decreases Ron decreases MOCVD, SiC substrate ns=9.75x1012(cm-2), µ=2109(cm2/Vs). S. Joglekar et al., TED, 2016

Purdue – GaN MOSHEMT SiC substrate ALD grown lattice-matched MgCaO improves on-off ratio and Dit ns=2x1013(cm-2), µ=1200(cm2/Vs). DC: Ron=1.3(Ω-mm), gm=475(mS/mm)@Ids=350mA/mm, Vgs~-3V, Vds=5V. H. Zhou et al., EDL, 2016 InAlN/GaN vs. AlGaN/GaN: Larger spontaneous polarization difference Higher 2DEG density 2. Limited SBH and thinner barrier Higher Leakage

UND – GaN HEMT Utilized AlN substrate instead of SiC due to: wide Eg (6.2 eV vs. 3.3 eV) lower dislocation density 104 cm-2 vs. 109 cm-2) Comparable thermal conductivity (340W/m.K vs. 370 W/m.K) MBE ns=3.4x1013(cm-2), µ=180(cm2/Vs). DC: Ron=1.8(Ω-mm), gm=250(mS/mm)@Vgs=-6.8V, Vds=8V fT=120GHz, fmax=24GHz@Vgs=-7.8V, Vds=8V M. Qi et al., APL, 2017. MOCVD, SiC substrate ns=1.92x1013(cm-2), µ=1240(cm2/Vs). DC: Ron=0.16(Ω-mm), gm=653(mS/mm)@ Vgs=-3.6V, Vds=3V fT=400GHz@Vgs=-3.6V, Vds=3V fmax=33GHz (high resistance of gate geometry) Y. Yue et al., JJAP, 2013.

UCSB – GaN MISHEMT N-polar GaN: improved electron confinement, lower RC (no AlGaN) MBE, sapphire substrate DC: Ron=0.29(Ω-mm), gm=480(mS/mm)@Vgs=-4.5V, Vds=8V fT=144GHz@Vgs=-4.5V, Vds=8V, fmax=400GHz@Vgs=-4V, Vds=8V S. Dasgupta et al., APL, 2010 & D. Denninghoff et al., DRC, 2012 MBE, SiC substrate, N-polar GaN DC: Ron=0.4(Ω-mm), gm=592(mS/mm) fT=160GHz, fmax=270GHz PAE=27.8%, Pout=3.13W/mm@Vg=-3V, Vds=9V, Ids=650mA/mm Operated in W-band (96GHz) B. Romanczyk et al., IEDM 3.5, 2016

Fujitsu – GaN HEMT SiC substrate InAlGaN barrier was used instead of InAlN: Reduced gate leakage. 90% more 2DEG density. Double layer SiN => prevent oxidation and reduce current collapse. fmax=200GHz Pout=3W/mm @ 96 GHz (W-band), @Vg=-1V, Vds=20V K. Makiyama et al., IEDM 9.1, 2015

Panasonic – GaN HEMT MOCVD, GaN substrate ns=5.6x1012(cm-2), µ=1900(cm2/Vs). Thick buffer layer (16µm) reduced output capacitance. => Faster switching GaN substrate improves crystal quality Suppress current collapse. BV up to 2800V@Lgd=20µm (Ec=1.4MV/cm) H. Handa et al., IEDM 10.3, 2016. MOCVD, GaN substrate, vertical structure ns=6.1x1012(cm-2), µ=1690(cm2/Vs). Slanted channel results in larger VT C-doped GaN/p-GaN well hybrid barrier layer (HBL) boosts BV to 1700V. Regrown triple layer further reduce Ron D. Shibata et al., IEDM 10.1, 2016.

HRL – GaN HEMT (T3 Generation) Left: E-band (83GHz) 3-stage PA, measured Pout=1.37W, PAE=27% Right: G-band (180GHz) 1-stage amplifier, Pout=0.296W, PAE=3.5% DC: Ron=0.81(Ω-mm), gm=723(mS/mm)@Vgs=-1.75V, Vds=6V A. Margomenos et al., CSICS, 2014 MBE, SiC substrate ns=1.3x1013(cm-2), µ=1200(cm2/Vs), BV= 42V. DC: Ron=0.81(Ω-mm), gm=723(mS/mm)@Vgs=-1.75V, Vds=6V fT=220GHz@Vgs=-1.75V, Vds=2V fmax=400GHz@Vgs=-1.5V, Vds=6V K. Shinohara et al., IEDM 30.1, 2010

HRL – GaN HEMT (T4 & T4A Generation) Lateral S/D scaling reduces Ron and improves fT. But scaled Lgd causes short-channel effect and reduce BV and fmax. Independently control of Lgs and Lgd by different sidewall thickness. BV=17V@Lg=20nm, Lgs=30nm, Lgd=80nm (Ec=2.13MV/cm) Ron=0.34(Ω-mm), gm~1.5S/mm fT=310GHz, fmax=582GHz@Vgs=0V, Vds=4V Ka-band (32GHz) 1-stage MMIC PA with a 59% PAE was demonstrated. K. Shinohara et al., TED, 2013, 2012 & M. Micovic et al., IEDM 3.3, 2016 ns~1.2x1013(cm-2), µ~1200(cm2/Vs) for both E/D-mode. E-mode @Lg=20nm,Lsw=70nm, BV=14V (Ec=2MV/cm) fT=342GHz, fmax=518GHz@Vgs=0.25V, Vds=4V D-mode @Lg=20nm,Lsw=50nm, BV=14V (Ec=2MV/cm) Ron=0.26(Ω-mm), gm=1.36S/mm@Vgs=-0.8V, Vds=4V fT=454GHz, fmax=444GHz@Vgs=-0.75V, Vds=3V K. Shinohara et al., IEDM 27.2, 2012 & Y. Tang et al., EDL, 2015

Summary

Thank you for your attention

Supplementary To boost fT: Reduce L, increase VGS-VT and mobility       To boost fT: Reduce L, increase VGS-VT and mobility To boost efficiency: Eliminate surface/bulk traps (passivation, growth), decrease leakage.

http://www.ee.sc.edu/personal/faculty/simin/ELCT871/18%20AlGAN-GaN%20HEMTs.pdf