Anomalous Source-side Degradation of InAlN/GaN HEMTs under ON-state - PowerPoint PPT Presentation

Anomalous Source-side Degradation of InAlN/GaN HEMTs under ON-state Stress Yufei Wu, Jesús A. del Alamo Microsystems Technology Laboratories, Massachusetts Institute of Technology October 04, 2016 Sponsor: NRO Contract No. DII NRO000-13C0309 1 Collaborator: Jose Jimenez (Qorvo)

Outlin line 1. Motivation 2. Source-side degradation under ON-stress 3. Gate leakage current and its temperature dependence 4. Positive gate stress 5. Conclusions 2

Motivation: InA nAlN as ba barrier er In 0.17 Al 0.83 N Al 0.2 Ga 0.8 N/GaN ln 0.17 Al 0.83 N/GaN Δ P 0 (e ⋅ cm -2 ) 6.5 x 10 12 2.7 x 10 13 P piezo (e ⋅ cm -2 ) 5.3 x 10 12 0 P total (e ⋅ cm -2 ) 1.2 x 10 13 2.7 x 10 13 [J. Kuzmik, EDL 2001] • High spontaneous polarization in InAlN  high 2DEG density [M. A. Laurent, JAP 2014] • InAlN thickness scaling  gate length scaling  W- and V-band applications In 0.17 Al 0.83 N lattice matched to GaN  Potentially better reliability! 3

Motivation: InA nAlN as ba barrier er InAlN/GaN HEMTs • W-band • E-mode Four gate geometries: • W g = 8 X 25 µm • W g = 8 X 50 µm • W g = 2 X 25 µm • W g = 2 X 50 µm Thermal models available [Saunier, CSICS 2014] 4

High-V DS Hi DS -hi high-I D stre ress Stress and characterization conditions: V DS,stress = 25 V, I Dstress = 400 mA/mm (V G ~ 1.5 V), 5 mins, RT (T j ~ 136 ° C) • • Characterization: @ 25 ° C after thermal detrapping 2 10 800 1 10 0 I D (mA/mm) 10 600 I D (mA/mm) -1 10 -2 400 10 V GS = 2 V -3 10 200 -4 10 -5 10 0 before stress -6 10 V DS = 0.1 V after stress -200 -7 10 0 1 2 3 4 -2 -1 0 1 2 V DS (V) V GS (V) Permanent degradation: • Significant I Dmax degradation • Δ V T > 0 • Significant I Doff degradation 5

Hi High-V D -high gh-I D stre ress After thermal detrapping, gate current degradation: -1 10 I G , I S after stress -3 10 • Large increase in I G after stress -5 • After stress: I G = I S >> I D in forward and 10 I D after stress |I| (A) reverse bias -7 10 I G before stress • Source-side damage unexpected! -9 10 I S before stress • Uncommon but previously observed in I D before stress 10 -11 V DS = 0 V AlGaN/GaN HEMTs [J. Joh, IEDM 2010] -6 -4 -2 2 0 V G S (V) 6

Tem emperature dep e dependen ence of ce of I I G and I nd I D -1 -1 10 T-dependence of I D : 10 T-dependence of I G : -3 -3 10 10 After stress T = -50 C T = -25 C -5 -5 T = -50 C 10 10 After stress T = 0 C T = -25 C |I D | (A) |I G | (A) T = 25 C T = 0 C -7 T = 25 C -7 T = 50 C 10 10 T = 50 C T = 75 C Before stress T = 75 C T = 100 C Before stress -9 T = 100 C -9 10 10 T = 125 C T = 125 C T = 150 C T = 150 C T = 175 C T = 175 C 10 -11 10 -11 V DS =0 V DS =0 T = 200 C T = 200 C -6 -4 -2 -6 -4 -2 0 2 0 2 V V G S (V) G S (V) Before stress: • For moderate V GS , negative T coefficient  thermionic emission limited current • I S behaves similar to I G After stress: • Significantly reduced T dependence for I G and I S • I D less affected  degradation on source side 7

HRT RTEM o of a v virg rgin de devi vice ce Virgin device Virgin device drain side source side Gate metal Gate metal passivation passivation InAlN InAlN AlN AlN GaN GaN Residual oxide? Gate recessed to the AlN interlayer 8

HRTEM of of stres essed de ed devi vice ce Stressed device Stressed device drain side source side Gate metal Gate metal passivation passivation InAlN InAlN AlN AlN GaN GaN Disordered region in GaN channel at 9 gate edge on source side

Hypothes esis f for or D Damage High V DS,stress + high I Dstress  high I Gstress too  high I GS  high T j  high electric field across AlN barrier on source side Conditions favor defect formation in AlN barrier on source side  I GS ↑ Also, gate sinking  Δ V T >0 10

Pos ositive V e V G step-stre ress-rec ecovery e exper periment Stress and characterization conditions: • V GS,stress = 0 - 2.5 V, V DS,stress = 0 V, step = 0.1 V, RT (T j ~ 48 ° C) • Characterization: @ 25 ° C after thermal detrapping before stress 3 10 after stress, detrapped 800 2 10 600 I D (mA/mm) 1 I D (mA/mm) 10 400 0 10 200 -1 10 0 -2 10 V GS = 2 V -200 V DS = 4 V -3 10 0 1 2 3 4 -2 -1 0 1 2 V DS (V) V GS (V) Permanent degradation: • Significant I Dmax degradation • Δ V T > 0 • Significant I Doff degradation 11

Time e evol olution of of I Dmax ax and nd I Goff ff Stress conditions: • V DS,stress = 0 V, V GS,stress = 0.1 – 2.5 V in 0.1 V steps • stress time = recovery time = 150 s; characterization every 15 s • RT V Gstress (V) V Gstress (V) 0.9 2.1 0.1 0.5 1.3 1.7 2.5 0.1 0.5 0.9 1.3 1.7 2.1 2.5 2 10 750 stress 1 10 700 recovery I Dmax (mA/mm) final |I Goff | (mA/mm) 0 650 10 I Dmax @ V GS = 2 V, V DS = 4 V I Goff @ V GS = -2 V, V DS = 0.1 V detrapped 600 -1 10 1.7 V 550 -2 10 final 500 stress -3 detrapped 10 2.3 V 450 recovery -4 10 400 0 2400 4800 7200 0 2400 4800 7200 time (s) time (s) • |I Goff | starts to increase from V GS,stress ~ 1.7 V  trap generation in AlN • I Dmax starts to severely degrade from V GS,stress ~ 2.3 V  gate sinking 12

Time e evol olution of of I Gstre ress Stress conditions: • V DS,stress = 0 V, V GS,stress = 0.1 – 2.5 V in 0.1 V steps • stress time = recovery time = 150 s; characterization every 15 s • RT V GStress (V) V GStress (V) 0.1 0.5 0.9 1.3 1.7 2.1 1.3 1.5 1.7 1.9 2.1 2.3 3 10 3 10 2 10 1 10 0 10 I Gstress (mA/mm) I Gstress (mA/mm) -1 10 -2 10 2.3 V -3 2 10 10 -4 10 -5 10 -6 10 -7 10 -8 10 1 10 0 1200 2400 3600 4800 6000 7200 3600 4800 6000 7200 time (s) time (s) • I Gstress increase becomes significant for V GS,stress ≥ 2.3 V 13

Gate e cur urrent degr degradation After thermal detrapping, gate current degradation: -1 10 -3 I G 10 After stress I S , I D I G -5 10 I S , I D |I| (A) -7 10 Before stress -9 10 10 -11 V DS =0 -6 -4 -2 0 2 V G S (V) • Symmetric degradation: I S ≈ I D ≈ I G /2 • Reproduced degradation signature of high-V DS -high-I D stress: high forward V G leads to increase in I G 14

HRTEM of of stres essed de ed devi vice ce Stressed device Stressed device drain side source side Gate metal Gate metal Gate metal passivation InAlN AlN InAlN GaN GaN Disordered region in GaN channel at gate Disordered region in GaN channel at 15 edge on drain side gate edge on source side

Conclus usions ns • Permanent degradation after High-V DS -high-I D stress: o I Goff ↑↑  Defect formation in AlN barrier on source side o Δ V T > 0, I Dmax ↓↓  Gate sinking o Affects source side • Positive gate stress: o Reproduced degradation signature of high-V DS -high-I D stress: I Goff ↑↑ , Δ V T > 0, I Dmax ↓↓ o I S ~ I D ~ I G /2  Symmetric degradation on source and drain side 16

Thank y k you & Questions? ? 17