UCSUCSBUCSB - University of California, Santa Barbara · BFOM = Baliga’s figure of merit for...

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U.S. Department of Defense

AlGaN/GaN HEMTs and AlGaN/GaN HEMTs and HBTsHBTs

Umesh K. Mishra

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PART IPART I

AlGaN/GaN HEMTsAlGaN/GaN HEMTs

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1500

260

5000

1300

µµµµ TmaxJFMRatio

BFOMRatio

EgεεεεMaterial

9.5

9.7

13.1

11.4

700 C8024.63.4GaN

600 C603.12.9SiC

300 C3.59.61.4GaAs

300 C1.01.01.1Si

BFOM = Baliga’s figure of merit for power transistor performance [K*µ*Ec3] JFM = Johnson’s figure of merit for power transistor performance

(Breakdown, electron velocity product) [Eb*Vbr/2π]

Materials Properties Comparison

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NeedNeed Enabling FeatureEnabling Feature Performance AdvantagePerformance Advantage

High LinearityHigh Frequency

Technology Leverage

High TemperatureOperation

HEMT Topology

High Electron Velocity

Wide Bandgap

Direct Bandgap: Enabler for Lighting

High Power/Unit Width Wide Bandgap, High Field Compact, Ease of Matching

High Efficiency High Operating Voltage Power Saving, Reduced Cooling

Optimum Band Allocation

Bandwidth, µ-Wave/mm-Wave

Rugged, Reliable, Reduced Cooling

Driving Force for Technology:Low Cost

High Voltage Operation High Breakdown Field Eliminate/Reduce Step Down

Low Noise High gain, high velocity High dynamic range receivers

Thermal Management

SiC Substrate High power devices with reduced cooling needs

NeedNeed Enabling FeatureEnabling Feature Performance AdvantagePerformance Advantage

High LinearityHigh Frequency

Technology Leverage

High TemperatureOperation

HEMT Topology

High Electron Velocity

Wide Bandgap

Direct Bandgap: Enabler for Lighting

High Power/Unit Width Wide Bandgap, High Field Compact, Ease of Matching

High Efficiency High Operating Voltage Power Saving, Reduced Cooling

Optimum Band Allocation

Bandwidth, µ-Wave/mm-Wave

Rugged, Reliable, Reduced Cooling

Driving Force for Technology:Low Cost

High Voltage Operation High Breakdown Field Eliminate/Reduce Step Down

Low Noise High gain, high velocity High dynamic range receivers

Thermal Management

SiC Substrate High power devices with reduced cooling needs

Advantages of WBG Devices

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GaAsGaAs High PowerAmplifier Module

EquivalentHigh Power

GaNGaN AmplifierModule

IN

OUT

IN

OUT

• 10-x power density ( > 10 W/mm)

• 10-x reduction in power-combining

• Improved efficiency (> 60 %)

• Improved reliability

• Compact size

• Superior Performance at reduced costGaAsGaAs High PowerAmplifier Module

EquivalentHigh Power

GaNGaN AmplifierModule

IN

OUT

IN

OUT

IN

OUT

IN

OUT

• 10-x power density ( > 10 W/mm)

• 10-x reduction in power-combining

• Improved efficiency (> 60 %)

• Improved reliability

• Compact size

• Superior Performance at reduced cost

Example of Advantage of WBG Devices

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S C X Ku K Ka Q V W

0.1

1

10

100

1000

Frequency Band

MissileSeekers

ShipRadar

LMDS MVDS

DigitalRadio CAR

Airborne Radar

THAAD Navy Decoy

LONGBOW

BATP31

Satcom

VSAT

Base Station

SatcomWat

ts

Base StationDriverAmp

Shipboard Radar,DD21

MMDS,WLL3G

UNIIHiperlan

2 GHz 10 GHz 30 GHz 60 GHz

Military

Commercial

S C X Ku K Ka Q V W

0.1

1

10

100

1000

Frequency Band

MissileSeekers

ShipRadar

LMDS MVDS

DigitalRadio CAR

Airborne Radar

THAAD Decoy

BATP31

Satcom

VSAT

Base Station

SatcomWat

ts


Shipboard RadarShipboard Radar

MMDS,WLL3G

UNIIHiperlan


Military

Commercial

S C X Ku K Ka Q V W

0.1

1

10

100

1000

Frequency Band

MissileSeekers

ShipRadar

LMDS MVDS

DigitalRadio CAR

Airborne Radar

THAAD Navy Decoy

LONGBOW

BATP31

Satcom

VSAT

Base Station

SatcomWat

ts


Shipboard Radar,DD21Shipboard Radar,DD21

MMDS,WLL3G

UNIIHiperlan


Military

Commercial

S C X Ku K Ka Q V W

0.1

1

10

100

1000

Frequency Band

MissileSeekers

ShipRadar

LMDS MVDS

DigitalRadio CAR

Airborne Radar

THAAD Decoy

BATP31

Satcom

VSAT

Base Station

SatcomWat

ts



MMDS,WLL3G

UNIIHiperlan


Military

Commercial


MMDS,WLL3G

UNIIHiperlan


Military

Commercial

Application Space

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Ball and Stick Diagram of the GaN Crystal

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Polarization World

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AlxGa1-x N

GaN

+ + + + + + + + + + +

+ + + + + + + + + + +

,Q AlGaNπ−

,Q AlGaNπ

,Q GaNπ−

,Q GaNπ

⇒⇒⇒⇒ + + + + + + + + + + +( ) ( )( ) ,,x GaNAlGaNP Q Qπ π= + −

includes the contribution of spontaneous and piezo-electric contributionsQπ

How does the electron gas form in AlGaN/GaN structures? - A

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GaNAlGaN

sp 2( )Q cmπ−

sn2( )Q cmπ−−

vE∆

,Eg GaN

l , Maximum Dipole MomentA GaN g GaN vV E E+ ∆ =!

How does the electron gas form in AlGaN/GaN structures? - C

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EFGaNAlGaN

EDD

DDN + 2( )Q cmπ−

Qπ−sn

How does the electron gas form in AlGaN/GaN structures? - D

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• High density 2DEG mobility limited by alloy scattering.

• Introduce thin AlN interlayer – remove alloy scattering by pushing 2DEG wavefunction out of the alloy region.

• Very useful result for attaining high conductivity 2DEG channels for HEMTs.

Application of AlGaN/GaN 2DEG transport studies

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• MBE growth of AlN/GaN structures is performedon GaN “templates” – thick GaN layers grown by MOCVD on (0001) sapphire

• Templates of two types are employed:(a) unintentionally doped GaN

(dislocation density: ~ 5x108 – 109 cm-2) (b) semi-insulating GaN

(dislocation density: ~ 1010 cm-2)

AFM image of type (a)GaN template

(0001) Sapphire

MOCVD GaN~ 2-3 µµµµm

MBE GaN~ 0.3 µµµµm

AlN d: 24 –50 Å

• Ga-stable growth (III/V flux ratio > 1)

• TS ~ 740 oC

RF Plasma-Assisted Molecular Beam Epitaxy of AlN/GaN Heterostructures

ONR/MURIONR/MURIONR/MURIONR/MURIIMPACT CenterIMPACT CenterIMPACT CenterIMPACT Center

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AlN/GaN Structures Grown on Semi-Insulating GaN Templates

1

1.5

2

2.5

3

3.5

4

20 25 30 35 40 45 50

300 K77 K

NS (1

0 13

cm-2

)

AlN thickness (A)

0

1000

2000

3000

4000

5000

20 25 30 35 40 45 50

300 K77 K

Mob

ility

µ (c

m2 /V

s)

AlN thickness (A)

• Both room-temperatureand 77 K electron mobility decrease drastically as AlNbarrier width increases

• 2DEG sheet density reaches the value of 3.65x1013 cm-2

in the AlN/GaN structure with a 49 Å barrier


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AlN/GaN Structures Grown onUnintentionally Doped GaN Templates

1

10

1000

104

10.00 100.0

10100

NS (1

013 c

m-2

) µ (cm2/Vs)

1000/T (K-1)

T (K)

d ~ 35 Ad ~ 45 A

AlN ~ 35 Åµ(300 K) = 1460 cm2/Vs

N2DEG ª NS(20 K) = 2.2x1013cm-2

AlN ~ 45 Åµ(300 K) = 1230 cm2/Vs

N2DEG ª NS(20 K) = 2.7x1013cm-2

AlN ~ 50 Åµ(300 K) = 330 cm2/Vs; NS(300 K) = 5.6x1013cm-2

µ(77 K) = 660 cm2/Vs; NS(77 K) = 3.6x1013cm-2

Pessimistic estimate of the2DEG sheet resistance at 300 K:

R < 200 Ω/


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Atomic Force Microscopy of AlN/GaNHeterostructures

1 µµµµm

0 nm

3 nm

AlN: 24 Å

AlN: 37 Å

AlN: 49 Å

Cracks in AlN layer

Tensile strain relaxation processbegins at d ~ 49 Å


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Polarization doping – concept and demonstration

• 3D electron slab by Polarization doping demonstrated.

• Carrier density verified by self –consistentSchrodinger – Poisson calculations.

• How do transport properties of the3DES compare to the donor doped and 2DEG counterparts ?

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Comparison of transport properties

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DC Device Level Issues (HEMTs)

If it ain’t good @ DC it ain’t goin’ to be good @ RF

SG

D

• Maximize I ⇒ Maximize nS, ν

• Maximize nS ⇒ Maximize PSP, PPE⇒ Maximize Al mole fraction

without strain relaxation

• Mazimize ν ⇒ Minimize effective gate length

⇒ Minimize Lg and gate length extension

• Maximize µ ⇒ Minimize dislocations⇒ Smooth interface

- - - - - - - - - - - - -AlGaN PSP + PPE

+ + + + + + +

Lg

GaN

Vmax

Imax

V

- - - - - - - - - - - - - - - - - - - -

max max max18

S

P V II V n υ= ⋅= ⋅ ⋅

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25 nm Al0.3Ga0.7N

1 nm AlN

UID GaN

SiC Substrate

Hall Data:

! Conventional Al0.3Ga0.7N/GaN HEMTns = 1.2 ×1013 cm-2

µ = 1200 cm2/V/s

! Al0.3Ga0.7N/AlN/GaN HEMTns = 1.65 ×1013 cm-2

µ = 1716 cm2/V/s

+ High charge

+ High mobility

AlGaN/AlN/GaN Heterostructure

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250 Å Al0.3GaN/GaN HEMT 250 Å Al0.3GaN/ 10 Å AlN/GaN HEMT

Band Diagram of AlGaN/AlN/GaN HEMT

! ns = 1.35×1013 cm-2! Higher charge: ns = 1.56×1013 cm-2

due to higher effective ∆∆∆∆EC

! Higher mobility due to the removal of alloy disorder scattering

-50 0 50 100 150 200 250 300 350 400 450 500-1

0

1

2

3

Thickness (A)

Ener

gy (e

V)

-50 0 50 100 150 200 250 300 350 400 450 500-1

0

1

2

3

Thickness (A)

Ener

gy (e

V)

Thin AlN

Effective ∆∆∆∆EC

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0.25 0.30 0.35 0.40 0.451.00E+013

1.50E+013

2.00E+013

2.50E+013

3.00E+013

2DEG

Den

sity

(cm

-2)

Al mole fraction x

Experiment Simulation

Sheet charge density vs. Al mole fraction

! Strongly dependent on the Al mole fraction

250Å AlxGa1-xN/10Å AlN/GaN

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0 20 40 60 80 100 120 140 160 180 200 2200.00E+000

5.00E+012

1.00E+013

1.50E+013

2.00E+0132D

EG D

ensi

ty (c

m-2)

Thickness of AlGaN (Å)

Experiment of AlGaN/AlN/GaN Simulation of AlGaN/AlN/GaN Simulation of AlGaN/GaN

Al0.37Ga0.63N/10Å AlN/GaN

! Weak function of AlGaN thickness! Faster saturation than conventional

AlGaN/GaN HEMT

ConventionalAlGaN/GaN

Sheet charge density vs. AlGaN thickness

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10 15 20 25 301.80E+013

2.00E+013

2.20E+013

2.40E+013

2DEG

Den

sity

(cm

-2)

Thickness of AlN (Å)

Simulation

250Å Al0.37Ga0.63N/ AlN /GaN

! 2DEG increases when AlN is thicker

Sheet charge density vs. AlN thickness

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-2 0 2 4 6 8 10 12 14 16

0

200

400

600

800

1000

gm = 200 mS/mm

∆∆∆∆VG = 1 VVG = 2 V

I D (m

A/m

m)

VDS (V)0 5 10 15 20 25 30

0

5

10

15

20

25

30

35 8.47 W/mm

PAE

(%)

Pout Gain PAE

Pout

(dBm

), G

ain

(dB)

Pin (dBm)

0

5

10

15

20

25

30

35

40

! 8.47 W/mm with a PAE of 28% @ 8GHz

! Bias: class AB at 45 V × 160 mA/mm

! Gate dimension: 0.7×150 µm2

! Imax = 950 mA/mm

! gm = 200 mS/mm

Device Performance of AlGaN/AlN/GaN HEMT

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Issues With Mazimizing Al Mole Fraction in AlxGa1-xN

Eg

Lattice Constant

GaN

AlN

InN

AlxGa1-xN

G

Pseudomorphic Relaxed with Misfit Morphology MediatedBy Dislocaton

DISLOCATIONS LEAD TO PREMATURE RELAXATION OF AlGaN AND A POTENTIAL RELIABILITY PROBLEM BECAUSE OF THE METALLIZED PITS

xAl = 0.2 xAl = 0.4 xAl = 0.6

250 nm 250 nm 250 nm

xHC= 0.3

relaxed

GaN

2.5 3 3.5

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Minimizing Gate Length Extension

ELECTRONS IN SURFACE STATES AND/OR BUFFER TRAPS DEPLETE THE CHANNEL CAUSING GATE LENGTH EXTENSION

SEVERE CONSEQUENCE: DISPERSION BETWEEN SMALL SIGNAL AND LARGE SIGNAL BEHAVIOR BECAUSE OF THE LARGE TRAP TIME CONSTANTS

Vds (V)

I d(5

mA

)

DC

AC

Load line

Dispersion

WHY DO THESE TRAPS ARISE?

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AlGaN

2DEG

SOURCE DRAINGATE

GaN

NucleationLayer

GaN, AlGaN or AlNSubstrate: Typically Sapphire or SiC

SiN Passivation

Schematic of Device Structure

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Vds (V)

I d(5

mA

)DC

AC

Load line

Dispersion

Dispersion in AlGaN/Ga HEMTs

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Lg

AlGaN

GATE

Electrons inSurface States

GaN

Source Drain

Depletion of 2DEGcaused by occupied

surface states

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Performance of Passivated AlGaN/GaN HEMT on Sapphire

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0

5

10

15

20

25

30

35

40

45

0 5 10 15 20 25 300

20

40

60

80

100

120

140

160PoutGainPAEId

Pin (dB)

Pou

t(d

B),

Gai

n(dB

), PA

E (%

)

I d(m

A)

Pout = 10.3 W/mmPAE= 41.6%

f=8GHz, Tuned for Power

0

5

10

15

20

25

30

35

40

45

0 5 10 15 20 25 300

20

40

60

80

100

120

140

160PoutGainPAEId

Pin (dB)

Pou

t(d

B),

Gai

n(dB

), PA

E (%

)

I d(m

A)

Pout = 10.3 W/mmPAE= 42%

f=8GHz, Tuned for Power

Performance of AlGaN/GaN HEMT on SiC (CLC)

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0

1

2

3

4

5

6

7

8

9

10

-5 0 5 10 15 20 25-30

-20

-10

0

10

20

30

40

50

60

70

Pin (dB)

P out

(W/m

m)

f=8GHz

PAE

(%)

Increasing Vds

PAE; Pout

0

1

2

3

4

5

6

7

8

9

10

-5 0 5 10 15 20 25-30

-20

-10

0

10

20

30

40

50

60

70

Pin (dB)

P out

(W/m

m)

f=8GHz

PAE

(%)

Increasing Vds

PAE; Pout

Drain Bias Dependence of Rf Power (CLC)

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Flip-chip AlGaN/GaN HEMT for Thermal Management

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Vds (V/divsion)

I d(A

/div

sion)

Vg start: +2V, Step: -2 V

I-V Curves from 8mm-wide HEMT

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Low Flip-chip Wide Bandwidth Amplifier

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0

5

10

15

20

25

30

35

40

18 22 26 30 34 38 4210

15

20

25

30

35

40

45

50GainDEPAEPout

Pin (dBm)

Gai

n (d

B),

DE

(%),

PAE

(%)

P out

(dBm

)

0

5

10

15

20

25

30

35

40

18 22 26 30 34 38 4210

15

20

25

30

35

40

45

50GainDEPAEPout

Pin (dBm)

Gai

n (d

B),

DE

(%),

PAE

(%)

P out

(dBm

)

Pulse Power Performance of mm-flipped Device

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20-Watt Broadband SiC MESFET Amplifier

• 22 W at P1dB across a 400 MHz band• Advantage of wide bandgap transistors: power-bandwidth

product greatly exceeding Si LDMOS

Balanced amplifier with Cree’s 10Balanced amplifier with Cree’s 10--Watt commercial FETs, CRF22010Watt commercial FETs, CRF22010

2

4

6

8

10

12

14

16

1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4Frequency (GHz)

Gain

(dB)

30

32

34

36

38

40

42

44

P1dB

(dBm

)

GainP1dBmW-CDMA

3GPP Test Model 1 with 16 DPCH

CREE, Inc.CREE, Inc.CREE, Inc.CREE, Inc.CREE, Inc.CREE, Inc.CREE, Inc.CREE, Inc.

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75-Watt SiC MESFET Amplifier

• 75 W CW, 11 dB gain demonstrated from a single SiC MESFET

• Currently being optimized for a 60-Watt Class A MESFET product, targeted for release by the end of the year

28 30 32 34 36 38 4040

42

44

46

48

50

Freq. = 2.0 GHz

Power

Input Power (dBm)O

utpu

t Pow

er (d

Bm

)

0

10

20

30

40

50

PAE

PA

E (%

)

2 GHz test fixture for 60 2 GHz test fixture for 60 W MESFET W MESFET developmentdevelopment


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10-Watt Broadband GaN HEMT Amplifier

• 11 W at P1dB across the 1.8 - 2.2 GHz band• 17 dB gain with only ±0.15 dB ripple

30

32

34

36

38

40

42

44

1.5 1.6 1.7 1.8 1.9 2 2.1 2.2 2.3 2.4Frequency (GHz)

P1dB

(dBm

)10

12

14

16

18

20

22

24

Small Signal G

ain (dB)

P1dB (dbm)SS Gain (dB)


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32 34 36 38 40 42 44

44

46

48

50 Pout Gain

Input Power (dBm)

Out

put P

ower

(dB

m)

0

5

10

15

20

25

30

35

40

Gain(dB

)

Demonstration of 100W CW GaN HEMT

•• Freq. = 2 GHzFreq. = 2 GHz•• VVDSDS = 52V= 52V•• Peak Drain Peak Drain EffEff. = 54%. = 54%•• 108 W achieved at P108 W achieved at P3dB3dB

103W @ 2.6 dB compression


Sponsored by Tom Jenkins, DUS&T/AFRL

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Summary of Technology Status

• Commercially-available SiC MESFETs

– 22 W broadband amplifier demonstrates power-bandwidth advantage of this technology

– 60 W Class A MESFET targeted for release by end of year

• GaN HEMTS on SiC Substrates

– excellent broadband and high power performance demonstrated

– emphasis of development is now on reproducibility and reliability

• SiC-based MMIC process developed for both technologies• 3-inch SI substrates will enable cost-competitive

manufacturing


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••Includes Includes ALL LEADINGALL LEADING players in the fieldplayers in the field••CREE = CREE = Cree LightingCree Lighting + + CreeCree--DurhamDurham

1996 1998 2000 2002

Total power

Year

Cree

Tot

al p

ower

(W)

HRL

CREE

Cree

UCSBCornell0

10

20

30

40

50

60

Early

Players

SapphireSiC

0

1

2

3

4

5

6

7

8

9

10

1996 1998 2000 2002Year

Pow

er d

ensi

ty (W

/mm

)

CREE

Cree

Cree

CornellUCSB

HRL

Early

Players

SapphireSiC

11 Power densityCornell

UCSB

NEC

••Includes Includes ALL LEADINGALL LEADING players in the fieldplayers in the field••CREE = CREE = Cree LightingCree Lighting + + CreeCree--DurhamDurham

1996 1998 2000 2002

Total power

Year

Cree

Tot

al p

ower

(W)

HRL

CREE

Cree

UCSBCornell0

10

20

30

40

50

60

Early

Players

SapphireSiC

0

1

2

3

4

5

6

7

8

9

10

1996 1998 2000 2002Year

Pow

er d

ensi

ty (W

/mm

)

CREE

Cree

Cree

CornellUCSB

HRL

Early

Players

SapphireSiC

11 Power densityCornell

UCSB

NEC

Power Performance vs. YearCree108W,CW Cree

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Part II

High Voltage Operation (> 330 V) of AlGaN/GaN HBTs

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Bipolar transistor key issues

• Injection

– γ"1– n " 1

[I=I0 exp (qv/nkt)]

Output ConductanceOutput Conductance– ∆∆∆∆IC/∆∆∆∆VCE """" 0

(∆∆∆∆WB/∆∆∆∆VCE """" 0)

CollectionCollection–Cbc """" 0– v"""" vsat [2 x 107 cm/s] (Kolnik et. al.)–Vbr """" Ecrit WC [Ecrit ~ 2 MV/cm] (Bhapkar and Shur.)

Subcollector

Base

Collector

EmitterTransportTransport

-- αααα """" 1

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Hurdles with GaN bipolar transistors

• Lack of low damage etch to reveal base

– Leaky E/B junction– Bad base contact– No etch stop

• High RB

– Poor p-GaN base contact– Low p-GaN base

conductivity• Deep acceptor (~160 meV)

Subcollector

Base

Collector

Emitter

Surface leakage Surface leakage due to etch damagedue to etch damage

Dislocation causes Dislocation causes leakageleakage

•• Hard to control junction placement in Hard to control junction placement in MOCVD due to memory effect of pMOCVD due to memory effect of p--dopantdopant MgMg

Low minority carrier Low minority carrier lifetimelifetime

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Demonstration of dislocation enhanced leakage

1 10-15

100 10-15

10 10-12

1 10-9

100 10-9

10 10-6

-20 -15 -10 -5 0 5 10 15 20

Leak

age

Cur

rent

[A]

Applied Bias [V]

Leakage from Collector to Emitter, Wing vs Window

LEO used to investigate leakage of devices LEO used to investigate leakage of devices without dislocations. (Lee McCarthy et al.)without dislocations. (Lee McCarthy et al.)

Dislocated

LEO

AFM scan of wing vs Window on LEO GaN

Regrowth Mask Regrowth MaskStandard template

LEO GaN

Results: LEO device demonstratedReduction in LeakageStable operation past 20VGain unchangedDevices on dislocated material also functional

ExplanationThick substrate sufficiently reduces

dislocations to prevent C/E short in window region

Gain (ττττe) not currently limited by dislocation density

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Strategy: Thick Collector

• Decent dislocation density

– High quality MOCVD templates achieved Dislocation density ~ 5e8 cm-2

• Low background doping

– ND < 1e16 cm-3 (Assuming uniform doping ND and Ecritical = 2 MV/cm, requires 10 µm to achieve 1 KV breakdown voltage.)

Doping vs. Depth (010704GA, 8 µµµµm collector)

1.E+14

1.E+15

1.E+16

1.E+17

0 1 2 3

Depth (µµµµm)

Dop

ing

(cm

-3)

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Emitter Regrowth Process Flow

• Selectively grow MOCVD emitter on base-collector structures.

1. Pattern regrowth mask2. Regrow emitter layer by

MOCVD3. Remove mask and contact

base and etch to collector4. Contact collector, emitter

n+ Subcollector

Sapphire Substrate

n- Collector

p Base

Mask

n+ Subcollector

Sapphire Substrate

n- Collector

p Base

n+

Emitter

n+ Subcollector

Sapphire Substrate

n- Collector

p Base

n+

Emitter

n+ Subcollector

Sapphire Substrate

n- Collector

p Base

n+

Emitter

1. 2.

3. 4.Pd/Au

Al/Au

Al/AuRegrown emitter

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Device structure

• Utilization of uid GaN spacer and grading layer

- HBTs with high emitter injection coefficiency• Etch damage and current mask layout limits Vbr

n+ Subcollector

Sapphire Substrate

1000 Å p Base

n+

Emitter

Sapphire2 µm GaN:Si (1e18 cm-3) subcollector

8 µm uid GaN (4e15 cm-3) collector

100 nm GaN:Mg (2e19 cm-3) base8 nm uid GaN spacer

8 nm GaN->Al 0.05 GaN (?3e18 cm-3) grading

4 nm GaN:Si (1e18 cm-3) contact4 nm Al 0.05 GaN->GaN:Si (1e18 cm-3) grading

105 nm Al 0.05 GaN:Si (1e18 cm-3) emitter

8 µm n- collector

Effective collector thickness ~ 2-3 µm

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HBT with 8 mm GaN collector

• Current gain (β) > 20• Common emitter operation > 300 V• Non-passivated • Base thickness 1000 Å• Al0.05GaN emitter Vbr ~330 V

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Summary

• Conclusion

– In selective emitter regrowth, a sharp Mg profile, ~ 40 nm/decade, enables the precise junction placement

– Improvement of regrown-emitter/base diodes

– Demonstration of high Vbr (> 300 V) with high β (DC common emitter operation up to 35)

UCSUCSBUCSB - University of California, Santa Barbara · BFOM = Baliga’s figure of merit for...

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