© 2017 HRL Laboratories, LLC. All Rights Reserved

Low-Cost Gallium Nitride Vertical

Transistor

HRL: Yu Cao, Mary Chen, David Chow, Rongming Chu, Kangmu Lee, Ray Li

Virginia Tech: Dushan Boroyevich, Rolando Burgos, Christina DiMarino, Amy Romero

March 24, 2017

© 2017 HRL Laboratories, LLC. All Rights Reserved

Project Objectives

1

• Objective: GaN vertical FET with 10X smaller power loss than Si IGBT

• Key Challenge: drift layer, gate structure, body contact, edge termination

© 2017 HRL Laboratories, LLC. All Rights Reserved

Team

2

3-phase inverter

800V 30kW 40kHzGaN vertical diode & transistor switch

GaN EPI, Device fabrication, Characterization Power Circuits/Modules

• HRL plans to demonstrate a high-performance GaN vertical transistor in a

circuit developed by Virginia Tech.

• The team will identify and retire critical technical risks associated with epitaxial

material growth, device design/fabrication, and circuit demonstration.

© 2017 HRL Laboratories, LLC. All Rights Reserved

GaN Trench MOSFET Process

3

3rd Year

Accomplishments

© 2017 HRL Laboratories, LLC. All Rights Reserved

IV Characteristics

4

3rd Year

Accomplishments

28 μm

0 1 2 3 4 50

1

2

3

VGS

= 0 ~ +10 V, 2 V step

RON

=1.7

I D (

A)

VDS

(V)

0 2 4 6 8 1010

-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

I D, I G

(A

)

VGS

(V)

VDS

= 1 V

ID

IG

0 100 200 300 400 500 60010

-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

Id, Ig

(A

)

Vds (V)

Vgs=0V

Id

Ig

Li, Ray, et al. "600 V/$1.7~\ Omega $ Normally-Off GaN Vertical Trench

Metal–Oxide–Semiconductor Field-Effect Transistor." IEEE Electron

Device Letters 37.11 (2016): 1466-1469.

600-V-Class normally-off transistor demonstrated.

© 2017 HRL Laboratories, LLC. All Rights Reserved

Temperature Dependent IV

5

0 2 4 6 8 100

1

2

3

4

5

6

I D (

A)

VDS

(V)

VGS

= 0, 1 , 2 , ... ,10 V

0 2 4 6 8 10100p

1n

10n

100n

1µ

10µ

100µ

1m

10m

100m

VDS

= 0.1 V

VGS

from 0 to 10V

22 oC

40 oC

70 oC

100 oC

125 oC

I D (

A)

VGS

(V)

100p

1n

10n

100n

1µ

10µ

100µ

1m

10m

100m

|IG| (A

)

20 40 60 80 100 120 1400

1

2

3

4

5

6

VDS

= 0.1 V

Up Sweep

Down Sweep

VT

H (

V)

Temperature (oC)

0 100 200 300 400 500 600100p

1n

10n

100n

1µ

10µ

100µ

1m

100 oC

70 oC

40 oCI D

, |I

G| (A

)

VDS

(V)

VGS

= 0 V

ID

|IG|

22 oC

20 40 60 80 100 120 1400.0

0.5

1.0

1.5

2.0

2.5

3.0

VGS

= 10V

VDS

= 0.1 V

VDS

= 1 V

RO

N (

ohm

)

Temperature (oC)

3rd Year

Accomplishments

• High on/off ration up to 125C.

• Positive temperature coefficient of Vth.

© 2017 HRL Laboratories, LLC. All Rights Reserved

Switching Characteristics

6

3rd Year

Accomplishments

Test Parameters

VDD 400 V

VGS 0 V to 8 V

ID up to 2 A

Rg 2.5, 5, 10 Ω

RShunt 100 mΩ

Turn on voltage slew rate: ~100V/ns

Next steps:

• Reduce pitch size

• Optimize drift layer mobility

• Demonstrate 800V/10A Switching

© 2017 HRL Laboratories, LLC. All Rights Reserved

Future Work

7

Project End Goals

1. Pitch Size• Reduce from 28um to 14um

2. Base Layer• Optimize thickness & doping

3. Drift Layer• Increase thickness from 8um to 16um

• Improve mobility to 1000 cm2/V-sec

4. Gate Trench• Accurate control of etch depth

• Round trench corner

5. Edge Termination

1. Pitch Size

2. Base Layer

3. Drift Layer

4. Gate Trench

5. E

dg

e T

erm

ina

tio

n

• HRL End of 2016 Measured: 1 mm2 chip, 800V/2A, 8~10 mohm-cm2, 400V/2A switching

• HRL End of 2017 Target: 1 mm2 chip, 1200V/10A, 2 mohm-cm2, 800V/10A switching

© 2017 HRL Laboratories, LLC. All Rights Reserved

Technology-to-Market

8

Technology-to-

Market

• Objective: mature the technology to TRL(through ARPA-E SWITCHES), then to

TRL7, then transition to manufacturing partners

• Target Market Segments: open to all market segments, pathway to automotive and

aerospace market is important

• Value Proposition: >2X better performance over SiC, at lower cost

• Supply Chain Challenge: flat, uniform, defect-free, and large GaN substrates

© 2017 HRL Laboratories, LLC. All Rights Reserved

Conclusions

9

• Demonstrated 600-V-class normally-off GaN vertical transistor

• Demonstrated fast switching at 400V/2AGaN

• Next step is to scale to 1200V/10A and demonstrate switching performance.