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CFES Annual Symposium April 12, 2019 T.P. Chow Smart Power Devices and ICs in GaN T. Paul Chow Rensselaer Polytechnic Institute Troy, NY 12180 E-mail: [email protected] 1

Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

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Page 1: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Smart Power Devices and ICs in GaN

T. Paul Chow Rensselaer Polytechnic Institute

Troy, NY 12180 E-mail: [email protected]

1

Page 2: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Outline

• Material Properties and Device Potentials • GaN Power Device Structures • HV Device Performance • Power ICs and Optoelectronic Integration • Summary

2

Page 3: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Widespread Application of GaN LEDs

Typical GaN LED schematic cross-section

(D. Hwang et al. Appl. Phys. Express, 2017) Backlighting

LED Headlights

Large Displays

LED Plant Growth (Wasabi)

Streetlights

Micro-LED

Display

Visible Light

Communication

(VLC)

Page 4: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Power Semiconductor Devices

4

Page 5: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Note: a – mobility along a-axis, c-mobility along c-axis, *Estimated value, **2DEG

Semiconductor Properties

• GaN grown on SiC can have a similar thermal conductivity as that of SiC • GaN grown on Si can reduce the wafer cost, have larger wafer size and use Si foundries for processing

5

Material Eg Direct/ ni er mn Ec vsat l

(eV) Indirect (cm-3) (cm2/V-s) (MV/cm) (107 cm/s) (W/cm-K)

Si 1.12 I 1.5x1010 11.8 1350 0.2 1.0 1.5

GaAs 1.42 D 1.8x106 13.1 8500 0.4 1.2 0.55

2H-GaN 3.39 D 1.9x10-10 9.9 1200a

2000** 3.3* 3.75a 2.5 2.5

4.1*

4H-SiC 3.26 I 8.2x10-9 10 720a 650c 2.0a 2.0 4.5

Diamond 5.45 I 1.6x10-27 5.5 3800 10 2.7 22

2H-AlN 6.2 D ~10-34 8.5 300 12* 1.7 2.85

Conventional Semiconductors

Wide Bandgap Semiconductors

Extreme Bandgap Semiconductors

Page 6: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow 6

Applications of Power Devices Modified from an Application Note of Powerex, Inc. Youngwood, PA. •Some devices are

pushing Si boundary

•SiC/GaN and

Diamond/AlN offer

promise for

improvement

GTO

DISCRETE

MOSFET

TRI-MOD

IGBT-MOD

MOSFET

MOD

TRANSISTOR

MODULES

IGBTMODTM

MODULES

100M

10M

1M

100

10

Po

wer

(V

A)

100K

10K

1K

10 100

Operation Frequency (Hz)

1K 10K 100K 1M

Page 7: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Vertical and Lateral Power Transistors

Lateral HEMT

Dra

in

So

urc

e

Gate

Page 8: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Vertical vs. Lateral Breakdown

0

200

400

600

800

1000

1200

1400

0 10 20 30 40 50 60 70 80

Bre

akd

ow

n V

olt

age

(V

)

Drift length (µm)

Si SOI oxide1.2um

Si SOI oxide1.6um

Si SOI oxide4.4um

Si SOI ideal

GaN epi 1um

GaN epi 2um

GaN epi 3um

GaN Ideal

8

Page 9: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Specific On-Resistance vs. Breakdown Voltage

• At 1000 V blocking voltage, projected lateral RESURF GaN specific on-resistance is 2 orders of magnitude lower than the Si lateral RESURF limit

• At above 1000 V blocking voltage, predicted on-resistance is close to the 1D 4H-SiC limit

1.0E-06

1.0E-05

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

1.0E+02 1.0E+03 1.0E+04Breakdown Voltage (V)

Sp

ec

ific

On

-re

sis

tan

ce

(oh

m-c

m2)

4H-SiC 1D

2H-GaN 1D

Silicon 1D

Si 2D RESURFSiC 2D RESURF

GaN 2D RESURF

Ron,sp ( BV )1.0-1.2

Page 10: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Lateral SiC and/or GaN Power Transistors

10

Source

Gate

Substrate (p+)

RESURF (n)

Silicon

Al0.05GaN

DrainSource

UID GaN

Gate

AlN/GaN Buffer

Silicon

UID Al0.05GaN

SiO2

DrainSource

UID GaN

GateUID Al0.25GaN

ILDUID GaN

AlN/GaN Buffer

HEMT/HFET RESURF MOSFET

MOSHC-HEMT/HFET MOSC-HEMT/HFET

Page 11: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

GaN Polarization Charges and 2DEG

* O. Ambacher et al., J. Appl. Phys. 85(6), 3222-3233 (1999).

• Net positive fixed charge (Qf) at AlGaN/GaN, due to the difference in spontaneous (PSP) and piezoelectric (PPE) polarization between GaN and AlGaN

• Qf can be controlled by Al mole fraction and thickness of AlGaN

• Qf of around 1013cm-2 is the desirable value for RESURF dose

11

Page 12: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

GaN 2DEG Mobility

12

Vitanov, SSE, 2010

Page 13: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Specific On-Resistance vs. Breakdown Voltage

13

Si IGBT Limit

Revised from N. Ikeda, ISPSD, 2008

RPI

Page 14: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Panasonic 600V GaN GIT

14

Current Collapse

No destruction and degradation was not observed up to 800V.

0

2

4

6

8

10

300 400 500 600 700 800

Drain-Source Voltage (V)

On-

resi

stan

ce (a

.u.)

Measured under the condition of practical use

Dyn

amic

on-

stat

e re

sist

ance

(a.u

.)

D

SG

FOM(Figure of Merit) RonA, RonQg

10 2 10 3 10 410-1

10 0

10 1

10 2

Breakdown voltage [V]

Spec

ific

On-

Res

ista

nce

Ron

A [

mcm

2 ]

10 5

10 3

10 4

Si Limit

Si Super Junction

MOSFET

Si IGBT

GaN Limit

Panasonic’s GaN-GIT

SiC Limit

10 2 10 3 10 410-1

10 0

10 1

10 2

Breakdown voltage [V]

Spec

ific

On-

Res

ista

nce

Ron

A [

mcm

2 ]

10 5

10 3

10 4

Si Limit

Si Super Junction

MOSFET

Si IGBT

GaN Limit

Panasonic’s GaN-GIT

SiC Limit

RonA and Breakdown Voltage State of art RonQg

Latest MOSFET

Panasonic GaN Transistor

Ron

Qg

Qg: Gate charge

4.03 nC

0.57 nC

1/7

D

SGFOM(Figure of Merit) RonA, RonQg

10 2 10 3 10 410-1

10 0

10 1

10 2

Breakdown voltage [V]

Spe

cific

On-

Res

ista

nce

Ron

A [

mcm

2 ]

10 5

10 3

10 4

Si Limit

Si Super Junction

MOSFET

Si IGBT

GaN Limit

Panasonic’s GaN-GIT

SiC Limit

10 2 10 3 10 410-1

10 0

10 1

10 2

Breakdown voltage [V]

Spe

cific

On-

Res

ista

nce

Ron

A [

mcm

2 ]

10 5

10 3

10 4

Si Limit

Si Super Junction

MOSFET

Si IGBT

GaN Limit

Panasonic’s GaN-GIT

SiC Limit

RonA and Breakdown Voltage State of art RonQg

Latest MOSFET

Panasonic GaN Transistor

Ron

Qg

Qg: Gate charge

4.03 nC

0.57 nC

1/7

D

SG

APEC, 2014

Page 15: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Cascode Switch

• Normally-off switch made with HV normally-on GaN HEMT

• Packaging cost and parasitics (inductances, thermal) make current up-scaling difficult

15

Page 16: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

High Voltage Stressing (HTRB)

Page 17: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Bi-Directional 600V GaN GIT

17

*Morita et al, IEDM 2007

Page 18: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Specific On-Resistance vs. Breakdown Voltage

• At 1000 V blocking voltage, ideal 1D GaN and AlN devices has more than three and four orders of magnitude lower specific on-resistance than silicon devices respectively

Ron,sp ( BV )2.4-2.6

1.0E-06

1.0E-05

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

1.0E+02 1.0E+03 1.0E+04Breakdown Voltage (V)

Sp

ec

ific

On

-re

sis

tan

ce

(oh

m-c

m2)

4H-SiC 1D

2H-GaN 1D

Silicon 1D

18

AlN 1D

Page 19: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

GaN Vertical Power UMOSFETs Benchmarking of reported GaN vertical power FETs • Ron,sp vs. BV of GaN vertical

power FETs are benchmarked

• Most vertical GaN devices exceed silicon limit and approach SiC limit

• However, fully-vertical devices are not integrable

• Very few reports on quasi-vertical structure; two reported

quasi-vertical UMOSFETs are

as follows:

• BV of 645 V; however, the gate trench area was used to calculate Ron,sp of 6.8 mΩ-cm2, which is incorrect

Liu et al (EPFL), IEEE Electron Device Lett. 2017

• No n- drift layer and hence not power FETs • No BV and Ron,sp reported; m-plane better than a-plane

Gupta et al (UCSB), Appl. Phys. Express 2016

Stripe-cell GaN quasi-vertical power UMOSFETs Hexagonal-cell GaN quasi-vertical UMOSFETs

Page 20: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Vertical Superjunction MOSFET

0.00 1.00 2.00Distance (Microns)

0.0

2.5

5.0

7.5

10.0

Dist

anc

e (M

icro

ns)

0.00 1.00 2.00

0.0

2.5

5.0

7.5

10.0

0.00 1.00 2.00

0.0

2.5

5.0

7.5

10.0

0.0

2.5

5.0

7.5

10.0

0 010 1050 50

100

500

100

500

Page 21: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

• Pillar dosage of GaN SJ structure optimized using simple diode structure. Doping unbalance effects was also examined.

• Keeping the optimized pillar dosage, pillar width and height were varied to obtain Ron,sp-BV trade-off design curves

GaN SJ diode structure BV and Ron,sp vs doping

Ron,sp vs BV for different doping Ron,sp vs BV for different pillar width and height

0

2000

4000

6000

8000

10000

12000

14000

0.0E+00

1.0E-02

2.0E-02

3.0E-02

4.0E-02

5.0E-02

6.0E-02

7.0E-02

8.0E-02

9.0E-02

1.0E-01

0.0E+00 5.0E+15 1.0E+16 1.5E+16 2.0E+16

Bre

akd

ow

n V

olt

age

(V

)

N-t

ype

GaN

Pill

ar R

on

,sp

(oh

m-c

m2)

Doping Concentration (cm-3)

Ron,sp

BV

1.0E-03

1.0E-02

1.0E-01

1.0E+00

1.0E+03 1.0E+04

Spe

cifi

c O

n-r

esi

stan

ce

(oh

m-c

m2)

Breakdown Voltage (V)

SiC 1D limit

GaN 1D limit

0

2000

4000

6000

8000

10000

12000

8.20

8.22

8.24

8.26

8.28

8.30

8.32

6 7 8 9 10 11 12 13 14B

reak

do

wn

Vo

ltag

e (

V)

N-t

ype

GaN

Pill

ar R

on

,sp

(mo

hm

-cm

2)

P GaN Doping Concentration (x 1015 cm-3)

Series2

BV

Ron,sp and BV of unbalanced SJ doping

1.0E-05

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

1.0E+03 1.0E+04 1.0E+05

Spe

cifi

c O

n-r

esi

stan

ce

(oh

m-c

m2)

Breakdown Voltage (V)

SJ only, pillar 8um

SJ only, pillar 5um

SJ only, pillar 3um

SJ only, pillar 1um

SiC 1D limit

GaN 1D limit

Design of GaN Superjunction FET

Z. Li, and T. P. Chow, IWN 2012

Page 22: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

1.0E-05

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

1.0E+03 1.0E+04 1.0E+05

Spe

cifi

c O

n-r

esi

stan

ce

(oh

m-c

m2)

Breakdown Voltage (V)

SJ diode, pillar 8um

SJ diode, pillar 5um

SJ diode, pillar 3um

SJ diode, pillar 1um

SJ HEMT, pillar 8um

SJ HEMT, pillar 5um

SJ HEMT, pillar 3um

SiC Thyristors

SiC 1D limit

GaN 1D limit• Designed

enhancement mode GaN vertical SJ HEMT with the optimized SJ structure using simulations:

• VTH of +1.3V • Ron,sp, for

example, of 4.2 mΩ-cm2 for BV of 12.4kV

• Design curve has

been obtained for different Ron,sp-BV trade-offs

Drain

P GaN

N+ GaN

N GaN

Source

GateP+ GaN

Source

N AlGaN

P+ GaN

GaN SJ vertical HEMT

-20

0

20

40

60

80

100

120

140

0 5 10 15 20 25 30

ID(m

A/m

m)

VD (V)

*Z. Li, and T. P. Chow, IWN 2012

Simulated output ID-VD

Simulated Ron,sp vs BV design curve

0

2000

4000

6000

8000

10000

12000

13.55

13.60

13.65

13.70

13.75

13.80

13.85

13.90

13.95

6 7 8 9 10 11 12 13 14

Bre

akd

ow

n V

olt

age

(V

)

Ro

n,s

p(m

Ω-c

m2)

P GaN Doping Concentration (x 1015 cm-3)

Ron,sp

BV

Ron,sp and BV of unbalanced SJ doping

Design of GaN Superjunction FET

Page 23: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

GaN Superjunction Devices

23

Amano, 2017

Page 24: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Performance of SiC and GaN SJ Devices

24

D. Disney, ISPSD, 2008

H. Ishida, EDL, 2008

• JFET effect limit the performance of conventional vertical superjunction device

• Natural polarization superjunction device uses intrinsic charge balance, no JFET region

Page 25: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Performance of SiC and GaN SJ Devices

25

• Keep dosage QSJ constant, shrinks pillar to increase doping concentration, also improve Ron,sp

• But more drift region consumed by depletion region when pillar width too small

Conventional Superjunction MOSFET

N+ substrate Drain

P

Source Gate

P-body

N+

N P N P N P N

Page 26: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Performance of SiC and GaN SJ Devices

26

• Keep dosage constant fixed charge at interfaces, shrinks pillar to reduce specific on-resistance

Natural Polarization Superjunction

MOSFET

Page 27: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Performance of SiC and GaN SJ Devices

27

• Numerical simulations verify the analytical model of optimum specific on-resistance

Page 28: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Performance of SiC and GaN SJ Devices

28

• 1D electric field profile along different symmetric lines in superjunction device

• BV usually happens along line #1 or #3 since electric field direction all vertical

• Electric field magnitude along line#2 is highest, but mostly horizontal

Page 29: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Performance of SiC and GaN SJ Devices

29

Page 30: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Performance of SiC and GaN SJ Devices

30

A. Nakajima, APL, 2006

• Natural polarization superjunction device, established by inherent spontaneous and piezoelectric polarization

• Use 2D Electron Gas (2DEG) and 2D Hole Gas (2DHG) for conducting current under forward bias

• Under reverse bias, intrinsic charge balance help drift region be depleted

• Nearly strain-free structures can be achieved by lattice-matching (LM) of AlInN/GaN heterostructures with the Indium mole fraction x = 0.18

Page 31: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Performance of SiC and GaN SJ Devices

31

• For 1 and 10kV devices, Ron,sp is about 3X and 100X lower for conventional 4H-SiC superjunction devices

• Ron,sp of vertical 2H-GaN SJ devices can reach 0.03 mΩ·cm2 and 1 mΩ·cm2 for breakdown of 1kV and 50kV

• For natural superjunction devices, Ron,sp reachs 0.06 to 3 mΩ·cm2 level for the BV range of 1kV to 50kV

Page 32: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

GaN Power ICs

32

Panasonic, ISSCC, 2014

700V, 93% efficient for 100W motor

Panasonic, IEDM, 2009

Page 33: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Monolithic Integration

33

Monolithic Integration Transistor

Objective: • Develop a process to enable monolithic integration of LEDs, control logic and power transistors. This IC will have the full spectrum of smart lighting features for a wider variety of applications due to reduced package size and cost and improved reliability.

SL-ERC Project S1.3.1: • Start date: July, 2010 • Duration: Through June, 2018

Page 34: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Optoelectronic Integration

34

SER: Grow wafers with necessary EPI layers, use subtractive etching to make components

Sapphire/Silicon

GaN

N-GaN

InGaN-GaN QW Layers

P-GaN

Buffer Al0.05GaN

Al0.21GaN GaN

P-GaN

Starting EPI MOS-HEMT Etch

CMOS Etch

N-FET P-FET

LED Etch

Advantages Risks High temperature steps of layer growth complete before processing

Thermal budget of processing may be incompatible

Highly non-planar, lithography obstacle Larger thermal path for cooling LEDs Need selective or high controlled etch to hit depth

Page 35: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

GaN Optoelectronic Integration • Literature review of GaN FET/LED monolithic integration

– Normally-on and normally-off HEMTs;

– Lateral and vertical MOSFETs; nanowire FETs

Page 36: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Integrated GaN Optoelectronics (Gen I)

36

• Successful demonstration of GaN LED driven by monolithically integrated GaN MOS-channel HEMT with selective epi removal

LED GaN MOSC-HEMT

Cathode

Anode

Drain Source

Gate

LED Epi

HEMT Epi

GND

Supply Voltage

Gate

LED

HEMTRPI, 2013

Page 37: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

*

Integrated GaN Optoelectronics (Gen I)

LED GaN MOSC-HEMT

Cathode

Anode

Drain Source

Gate

LED Epi

HEMT Epi

RPI, 2013

Page 38: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

RPI: GaN MOSC-HEMT/LED Integration

38

Page 39: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Integrated GaN Optoelectronics (Gen II)

39

• Successful demonstration of GaN LED driven by monolithically integrated vertical GaN UMOSFET with Selective Epi Removal (SER)

RPI, 2018

Page 40: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Integrated GaN Optoelectronics (Gen II)

40

RPI, 2018

Current and LOP vs. voltage LOP and EQE vs. current density

Page 41: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Integrated GaN Optoelectronics (Gen II)

41

RPI, 2018

Page 42: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Summary

• Lateral GaN p-HEMTs offer substantial performance advantages over Si

• Vertical superjunction GaN power FETs with polarization HJs are >1000X better

• Power ICs and Optoelectronic Integration have been demonstrated

42

Page 43: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Thank You!

43

Page 44: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

600V Power Device Comparison

Page 45: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

1.2 kV Power Device Comparisons

Device Ron,sp (mΩ.cm2)

VF (V)

Vth (V)

Esw (mJ/cm2)

ton (ns)

toff (ns)

Si UMOS FS-IGBT - 1.2 4 26.4 5 1230

SiC DMOSFET 2.3 - 2.3 0.85 1 30

GaN UMOSFET 1.5 - 4 0.5 4 40

GaN HEMT 0.9 - - 4.8 1.0 3.7 35

SiC and GaN unipolar switches can operate at much higher frequency – lower requirements on passive components

Page 46: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

SiC and GaN Power Device Commericalization

• SiC – 0.6-1.7kV Schottky, MOSFET and JFET – < 600V or > 1.7kV? – 10-25kV pin rectifier or IGBT?

• GaN – 30V HEMT – 400-600V HEMT – 1-1.2kV HEMT?

46

Page 47: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

*S.M. Goodnick et al., J. Vac. Sci.

Technol. B, vol. 1 (3), pp. 803-808, 1983.

GaN MOS vs. Si MOS

47

CitSRSPBtotal mmmmm

11111

itfT NNN

,)1(),( Cit

scrT

CitTCit

N

nT

NnN

m

B

B

ref

BND

T

mm

)/(1)/300(max

Bulk Mobility

3/1

TE

B

E

ASPm

Surface Phonon

2

E

SR

m

Surface Roughness Coulombic

Page 48: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Interface State Density Comparisons

EvSi EcSi Ec4H-SiCEv4H-SiC

1E10

1E11

1E12

1E13

EcGaNEvGaN

Interfacestateden

sity(cm

-2eV-1) Si

4H-SiCGaN

Page 49: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

JI, SOI and DI RESURF Junction Isolation (JI)

RESURF Silicon on Insulator (SOI)

RESURF Dielectric Isolation (DI)

RESURF

• Junction Isolation (JI) RESURF balance the ionized donor (ND

+) in n- drift region with ionized acceptors (NA-) in the p-

substrate.

• Silicon on Insulator (SOI) RESURF balance the ND+ in drift

region with electrons in the n+ substrate.

• Dielectric Isolation (DI) RESURF balance the ND+ with other

negative charges such as anode or field plates

49

Page 50: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Drift Region Optimization

Silicon

UID Al0.05GaN

SiO2

DrainSource

UID GaN

GateUID Al0.25GaN

ILD

AlN/GaN Buffer

Silicon

UID Al0.05GaN

SiO2

DrainSource

UID GaN

GateUID Al0.25GaN

ILDUID GaN

AlN/GaN Buffer

Without GaN cap With GaN cap

• Without GaN cap, interface charges between ILD and AlGaN make surface electric field uniformity difficult

• With GaN cap, charge balance in AlGaN layer and minimization of interface charges between ILD and GaN cap enhances surface electric field uniformity (Natural RESURF)

50

Page 51: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Enhancement Mode GaN Power Transistor

• Recessed channel – etch control • F implantation – epi dependent • MOS channel – low mobility and gate oxide

reliability • P-(Al)GaN gate – etch stop and damage • Back channel - structural and compositional

control • Cascoded HEMT – Packaging parasitics, device

matching and difficulty in current scale-up

51

Page 52: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow 52

Wch = 200 mm, Lch= 2 mm, LGS= 3 mm

• Breakdown voltage saturated over Lgd of 15 µm • Thicker Epi wafer => Higher Breakdown voltage • Growth of thick GaN epi or insulating buffer is the major limitation on breakdown voltage for devices of GaN on silicon • Specific on-resistances of 16.3-16.8m-cm2 have been obtained.

Buffer

Si(111) Substrate

GaN:Mg

DSAlGaNu GaN

G

① Breakdownbetween G-D

② Breakdown in epilayer

0

100

200

300

400

500

600

700

0 4 8 12 16 20 24 28 32 36Lgd (μm)

Bre

akdo

wn

Vol

tage

(V)

Thickness 4.4 mm

Thickness 2.6 mm

Furukawa MOS Channel-HEMT

Furukawa, ISPSD, 2009

Page 53: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

RPI MOSC-HEMT • BV = 350V

• Ron,sp=4.0mOhm-cm2 • VT=0.3V

RPI, ISPSD 2012

• Lch=0.3 um • Ldrift=8 um

53

-2.00E-02

0.00E+00

2.00E-02

4.00E-02

6.00E-02

8.00E-02

1.00E-01

1.20E-01

0 2 4 6 8 10 12 14 16

-1.00E-04

0.00E+00

1.00E-04

2.00E-04

3.00E-04

4.00E-04

5.00E-04

6.00E-04

0.00E+00 1.00E+02 2.00E+02 3.00E+02 4.00E+02

Id

Ig

Id

Ig

Id

Ig

MOS Channel-HEMT on Si

Page 54: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Current Collapse

54

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

0 10 20 30 40

DC

Cu

rren

t C

oll

ap

se

Ra

tio

RESURF length (um)

MOSHEMT on UID GaN

MOSHEMT on P GaN

• Current collapse measured on both GaN RESURF MOS-HEMT on UID and p GaN epi

• No correlation of current ratios for different RESURF length

• MOS-HEMTs on p GaN showed ratio close to 1, which is much less as compared with that of UID GaN

0 20 40 60 80 100 120

0.80

0.85

0.90

0.95

1.00

1.05

10 12 14 16 18 20 22 24 26

Channel length of Non-RESURF Device (um)

DC

Cu

rren

t C

oll

ap

se

Ra

tio

RESURF length of RESURF Device (um)

RESURF Devices

Non-RESURF Devices

• Current collapse measured on RESURF and non-RESURF MOS-HEMTs on p GaN

• Current ratio all close to 1, with little dependence on the MOS channel length for non-RESURF devices and the RESURF length for RESURF devices.

MOSC-HEMT on UID GaN vs. P GaN Non-RESURF vs. RESURF device

Page 55: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Current Collapse

55

GaN MOSFET GaN MOSC-HEMTs on UID

GaN vs. P GaN

*RPI, ISPSD 2010

Page 56: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Integrated GaN HEMT Cascoded Pair

56

UKNC,, ICNS, 2015

Page 57: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

GaN PWM IC

57

HKUST, ISPSD, 2014

Page 58: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

GaN PWM Power Converter

58

CPEC, CICC, 2015

Page 59: Smart Power Devices and ICs in GaN TPChow.pdfGaN epi 1um GaN epi 2um GaN epi 3um GaN Ideal. 8 . CFES Annual Symposium April 12, 2019 T.P. Chow . Specific On-Resistance vs. Breakdown

CFES Annual Symposium April 12, 2019 T.P. Chow

Optoelectronic IC Integration

59

Silicon

UID Al0.05GaN

SiO2

DrainSource

UID GaN

GateUID Al0.25GaN

ILDUID GaN

AlN/GaN Buffer

Left to Right: MOS-HEMT structure for GaN on Silicon, Current LED structure, Proposed GaN-CMOS structure.

Sapphire

GaN N-GaN

InGaN-GaN QW Layers

P-GaN

P-contact/spreading

N-contact

Drain Source Drain Source Source

Sapphire GaN

P-GaN N-GaN

gate gate

N-GaN P-GaN

The ability to use Silicon as a substrate for LEDs will lead to a lower overall cost. To prepare for this paradigm shift, we have included research on GaN-MOS-HEMTs built on a Silicon substrate.

GaN controls and power FETs will enable high frequency and high efficiency switching for data and power conversion applications