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

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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 Collaborator: Jose Jimenez (Qorvo)

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SLIDE 2

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

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SLIDE 3

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High spontaneous polarization in InAlN 

high 2DEG density

InAlN thickness scaling  gate length scaling

 W- and V-band applications

Al0.2Ga0.8N/GaN ln0.17Al0.83N/GaN Δ P0 (e⋅cm-2) 6.5 x 1012 2.7 x 1013 Ppiezo (e⋅cm-2) 5.3 x 1012 Ptotal (e⋅cm-2) 1.2 x 1013 2.7 x 1013 [J. Kuzmik, EDL 2001]

In0.17Al0.83N

In0.17Al0.83N lattice matched to GaN  Potentially better reliability!

[M. A. Laurent, JAP 2014]

Motivation: InA nAlN as ba barrier er

SLIDE 4

Motivation: InA nAlN as ba barrier er

[Saunier, CSICS 2014]

Four gate geometries:

Wg = 8 X 25 µm
Wg = 8 X 50 µm
Wg = 2 X 25 µm
Wg = 2 X 50 µm

Thermal models available

InAlN/GaN HEMTs

W-band
E-mode

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SLIDE 5

Hi High-VDS

DS-hi

high-ID stre ress

Stress and characterization conditions:

VDS,stress = 25 V, IDstress = 400 mA/mm (VG ~ 1.5 V), 5 mins, RT (Tj ~ 136 °C)
Characterization: @ 25 °C after thermal detrapping

1 2 3 4

200

200 400 600 800

VGS = 2 V

ID (mA/mm) VDS (V)

2
1

1 2 10

7

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10 10

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before stress after stress VDS = 0.1 V

ID (mA/mm) VGS (V)

Significant IDmax degradation
ΔVT > 0
Significant IDoff degradation

Permanent degradation:

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SLIDE 6

Hi High-VD-high gh-ID stre ress

After thermal detrapping, gate current degradation:

Large increase in IG after stress
After stress: IG = IS >> ID in forward and

reverse bias

Source-side damage unexpected!
Uncommon but previously observed in

AlGaN/GaN HEMTs [J. Joh, IEDM 2010]

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2

V

G S (V)

10 -11 10

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|I| (A)

IG, IS after stress ID after stress IG before stress IS before stress ID before stress

VDS = 0 V

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SLIDE 7

Tem emperature dep e dependen ence of ce of I IG and I nd ID

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2

2

V

G S (V)

10 -11 10

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|I G | (A)

T = -50 C T = -25 C T = 0 C T = 25 C T = 50 C T = 75 C T = 100 C T = 125 C T = 150 C T = 175 C T = 200 C

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2

2

V

G S (V)

10 -11 10

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|I D | (A)

T = -50 C T = -25 C T = 0 C T = 25 C T = 50 C T = 75 C T = 100 C T = 125 C T = 150 C T = 175 C T = 200 C

Before stress After stress After stress Before stress

VDS=0 VDS=0

T-dependence of IG: T-dependence of ID:

Before stress:

For moderate VGS, negative T coefficient  thermionic emission limited current
IS behaves similar to IG

After stress:

Significantly reduced T dependence for IG and IS
ID less affected  degradation on source side

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SLIDE 8

Virgin device source side Gate metal

Gate recessed to the AlN interlayer

InAlN passivation GaN AlN Virgin device drain side Gate metal InAlN passivation GaN AlN

Residual oxide?

HRT RTEM o

f a v

virg rgin de devi vice ce

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SLIDE 9

Disordered region in GaN channel at gate edge on source side

InAlN passivation GaN AlN Gate metal Stressed device source side Stressed device drain side InAlN passivation GaN AlN Gate metal

HRTEM of

f stres

essed de ed devi vice ce

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High VDS,stress + high IDstress high IGstress too  high IGS  high Tj  high electric field across AlN barrier on source side Conditions favor defect formation in AlN barrier on source side  IGS↑ Also, gate sinking  ΔVT>0

Hypothes esis f for

r D

Damage

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Pos

sitive V

e VG step-stre ress-rec ecovery e exper periment

Stress and characterization conditions:

VGS,stress = 0 - 2.5 V, VDS,stress = 0 V, step = 0.1 V, RT (Tj ~ 48 °C)
Characterization: @ 25 °C after thermal detrapping

1 2 3 4

200

200 400 600 800

VGS = 2 V

ID (mA/mm) VDS (V)

2
1

1 2 10

3

10

2

10

1

10 10

1

10

2

10

3

VDS = 4 V

ID (mA/mm) VGS (V)

before stress after stress, detrapped

Significant IDmax degradation
ΔVT > 0
Significant IDoff degradation

Permanent degradation:

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SLIDE 12

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Time e evol

lution of
f IDmax

ax and

nd IGoff

ff

|IGoff| starts to increase from VGS,stress ~ 1.7 V  trap generation in AlN
IDmax starts to severely degrade from VGS,stress ~ 2.3 V  gate sinking

Stress conditions:

VDS,stress = 0 V, VGS,stress = 0.1 – 2.5 V in 0.1 V steps
stress time = recovery time = 150 s; characterization every 15 s
RT

2400 4800 7200

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2.5 final detrapped stress recovery

|IGoff| (mA/mm) time (s)

2.1 0.1 0.5 0.9 1.3 1.7

VGstress (V)

2400 4800 7200

400 450 500 550 600 650 700 750

2.5

VGstress (V)

2.1 1.7 1.3 0.9 0.5 stress recovery

IDmax (mA/mm) time (s)

final detrapped 0.1

2.3 V 1.7 V IGoff @ VGS = -2 V, VDS = 0.1 V IDmax @ VGS = 2 V, VDS = 4 V

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3600 4800 6000 7200 10

1

10

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IGstress (mA/mm) time (s) VGStress (V)

1.3 1.5 1.7 1.9 2.1 2.3

2.3 V

Stress conditions:

VDS,stress = 0 V, VGS,stress = 0.1 – 2.5 V in 0.1 V steps
stress time = recovery time = 150 s; characterization every 15 s
RT
IGstress increase becomes significant for VGS,stress ≥ 2.3 V

1200 2400 3600 4800 6000 7200 10

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IGstress (mA/mm) time (s) VGStress (V)

0.1 0.5 0.9 1.3 1.7 2.1

Time e evol

lution of
f IGstre

ress

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V

G S (V)

10 -11 10

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|I| (A)

Gate e cur urrent degr degradation

After thermal detrapping, gate current degradation:

Symmetric degradation: IS ≈ ID ≈ IG/2
Reproduced degradation signature of high-VDS-high-ID stress:

high forward VG leads to increase in IG

Before stress After stress

VDS=0 IG IS, ID IG IS, ID

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SLIDE 15

Disordered region in GaN channel at gate edge on drain side

InAlN GaN Gate metal InAlN passivation GaN AlN Gate metal

Disordered region in GaN channel at gate edge on source side

Gate metal Stressed device source side Stressed device drain side

HRTEM of

f stres

essed de ed devi vice ce

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Conclus usions ns

Permanent degradation after High-VDS-high-ID stress:
IGoff ↑↑  Defect formation in AlN barrier on source side
ΔVT > 0, IDmax ↓↓  Gate sinking
Affects source side
Positive gate stress:
Reproduced degradation signature of high-VDS-high-ID stress:

IGoff ↑↑ , ΔVT > 0, IDmax ↓↓

IS ~ ID ~ IG/2  Symmetric degradation on source and drain side

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Thank y k you & Questions? ?

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