impact of high-power stress on dynamic on-resistance of high-voltage gan hemts

1

Impact of high-power stress on dynamic ON-resistance of

high-voltage GaN HEMTs

Donghyun Jin and Jesús A. del AlamoMicrosystems Technology Laboratory

Acknowledgement: ARPA-E ADEPT, SRC, DRIFT MURI

2

Outline

1. Motivation

2. Dynamic ON-resistance measurement

3. High-power stress experiment

4. Discussion

5. Conclusion

3

Motivation• Dynamic ON-resistance (RON) a.k.a. “current collapse”

Tirado et al, TED 2007

VDS

IDS

i) ION right afterOFF-state: RON ↑

ION initial

In OFF-to-ON switching

ii) Slow recovery of RON

4

Motivation• Dynamic ON-resistance (RON) a.k.a. “current collapse”

‒ Primary concern in GaN power-switching and RF power-amplifier devices

Tirado et al, TED 2007

VDS

IDS

i) ION right afterOFF-state: RON ↑

ION initial

In OFF-to-ON switching

ii) Slow recovery of RON

5

Motivation• Much less understanding

‒ Impact of electrical stress on dynamic RON

‒ Especially, high-power (HP) state in GaN device operation

6



‒ Especially, high-power (HP) state in GaN device operation < RF-amplifier > < Power-switching >

VDS

ID

RF load line

OFF

ON Hard-switching

VDS

ID

7




Meneghesso et al, TED 2006

8




• Goal‒ New methodology for dynamic RON measurement‒ Investigate the impact of high-power stress on dynamic RON

Meneghesso et al, TED 2006

9

Outline

1. Motivation



4. Discussion

5. Conclusion

10

Dynamic RON measurement• New methodology for RON transient measurement

from 200 ns to any arbitrary length of time‒ Auriga AU4750 pulsed-IV for RON(200 ns ≤ t ≤ 3 ms) +

Agilent B1500A SDA for RON(3ms < t )

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from 200 ns to any arbitrary length of time‒ Auriga AU4750 pulsed-IV for RON(200 ns ≤ t ≤ 3 ms) +

Agilent B1500A SDA for RON(3ms < t )

• Dynamic RON measurement from pulsed-IV

VDS

ID

OFF (VGSQ, VDSQ)

ION @ VGS= 1 V 1/RON

12


from 200 ns to any arbitrary length of time

VDS

t

VDSQ

VGS

1 V t

VGSQ

Synchronous switching of VGS and VDS

‒ Auriga AU4750 pulsed-IV for RON(200 ns ≤ t ≤ 3 ms) + Agilent B1500A SDA for RON(3ms < t )

• Dynamic RON measurement from pulsed-IV

VDS

ID

OFF (VGSQ, VDSQ)

ION @ VGS= 1 V 1/RON

13

0 1 2 3x 10-3

0

0.02

0.04

0.06

0.08

Time [sec]

I D [A

/mm

]

Dynamic RON measurement• RON(t) from ID(t)-VDS measurements

Q(VGSQ= -10 V, VDSQ= 50 V)

ID(200 ns ≤ t ≤ 3 ms) @ VGS= 1 V, VDS ≤ 1.2 V

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0 0.4 0.8 1.20

0.02

0.04

0.06

0.08

I D [A

/mm

]V

DS [V]

0 1 2 3x 10-3

0

0.02

0.04

0.06

0.08

Time [sec]

I D [A

/mm

]

Dynamic RON measurement• RON(t) from ID(t)-VDS measurements

Q(VGSQ= -10 V, VDSQ= 50 V)

1/RON

ID(t= 1 ms) @ VGS= 1 V

‒ Extract RON transients from 200 ns up to 3 ms in OFF-to-ON

ID(200 ns ≤ t ≤ 3 ms) @ VGS= 1 V, VDS ≤ 1.2 V

100 μs

10 μs

200 ns

15

Dynamic RON measurement

10-710-610-510-410-310-210-1 100 101 102 103 1043.5

4

4.5

5

5.5

Time [sec]

RO

N [

-mm

] Pulsed-IV

Q(-5 V, 40 V)

RON_DC= 3.5 Ω∙mm

* Virgin GaN-on-SiC HEMT sample 200 ns ≤ t ≤ 3 ms

16

10-710-610-510-410-310-210-1 100 101 102 103 1043.5

4

4.5

5

5.5

Time [sec]

RO

N [

-mm

]


Pulsed-IVSemiconductor Device Analyzer

200 ns ≤ t ≤ 3 ms 3 ms ≤ t ≤ 2.8 hr

Q(-5 V, 40 V)

RON_DC= 3.5 Ω∙mm

* Virgin GaN-on-SiC HEMT sample

OFF(-5 V, 40 V) to ON

17

10-710-610-510-410-310-210-1 100 101 102 103 1043.5

4

4.5

5

5.5

Time [sec]

RO

N [

-mm

]


Pulsed-IVSemiconductor Device Analyzer

200 ns ≤ t ≤ 3 ms 3 ms ≤ t ≤ 2.8 hr

Q(-5 V, 40 V)

RON_DC= 3.5 Ω∙mm

• RON transients over 11 decades in time→ details in DJin ISPSD 2012

* Virgin GaN-on-SiC HEMT sample


18

Outline

1. Motivation



4. Discussion

5. Conclusion

19

High-power DC-stress

0.1

1

10

100

0.6

0.7

0.8

0.9

1

1.1

1.2

0 10 20 30 40

I GO

FF[m

A/m

m]

RO

N/R

ON(0

), I D

MAX

/I DM

AX(0

)

High power ON-state stress time [min]

IDMAX

RON

|IGOFF|

* Constant HP-stress: VDS= 20 V, ID≈0.6 A/mm, P≈12 W/mm tstress= 10, 20, 30, 40 min (4 samples)

• Prominent degradation in RON and IDMAX; minor in IGOFF • Dynamic RON measurement after each HP-stress test

* tstress= 40 min sample

10-7 10-6 10-5 10-4 10-3 10-2 10-1 100 101 102 1030

2

4

6

8

10

12

Time [sec]

RO

N/R

ON

-DC

Dynamic RON transients

• Dynamic RON↑ ≥ 10 x RON_DC after 40 min HP-stress- Up to 30 min: minor increases in dynamic RON

• In contrast, small RON_DC↑ (16%)- minor permanent (non-transient) degradation

• Fast RON recovery in ms range in all cases

tstress= 40 min

3020

10Virgin

Transient from OFF (VGSQ= -10 V, VDSQ= 50 V) to ON (VGS= 1 V, VDS ≤ 1.2 V)

20

HP-stress time

RON_DC increase

10 7%

20 8%

30 11%

40 16%

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Time constant spectrum

10-7 10-6 10-5 10-4 10-3 10-2 10-1 100 101 102 103

0

0.2

0.4

0.6

0.8

[sec]

Am

plitu

de (a

i)40 min

3020

10 Virgin

iON

tiON ReaR i )/(

• 40 min HP-stress → fast transient with short time constants (μs ≤ τ ≤ ms) ↑

• In contrast, negligible changes in long time constants

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Dynamic RON at different T

• As T ↑, RON transients substantially accelerated • RON transients → conventional traps

10-7 10-6 10-5 10-4 10-3 10-2 10-1 100 101 102 1030

2

4

6

8

10

12

Time [sec]

RO

N/R

ON

-DC

10-710-610-510-410-310-210-11001011021030

10

20

30

40

50

Time [sec]

RO

N [

-mm

]T= 25 C45


65

85105125150

T ↑


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Time constant spectrum at different T

10-7 10-6 10-5 10-4 10-3 10-2 10-1 100 101 102 1030

0.5

1

1.5

2

2.5

[sec]

Am

plitu

de [A

.U.]

25 C

45 C

65 C

85 C

105 C

125 C

150 C

• Evolution of dominant time constant peaks at different T


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Arrhenius plot

• Dominant trap energy levels at 0.31, 0.45, 0.53 and 0.57 eV (below EC of AlGaN barrier)

• Responsible for dramatic increase in dynamic RON

-5

0

5

10

15

20

25 30 35 40 45 50 55

ln(T

2 τ) [

K2 s

]

1/kT [eV-1]

EA= 0.87 eV0.75 eV

0.57 eV

0.53 eV

0.45 eV

0.31 eV

0.23 eV

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Outline

1. Motivation



4. Discussion

5. Conclusion

26

10-6 10-5 10-4 10-3 10-2 10-1 100 101 102 1031

2

3

4

5

Time [sec]

RO

N/R

ON

-DC

Virgin

After 3 min HP-stress with VDS= 30 V, P≈ 9 W/mm

Transient from OFF (-10 V, 50 V) to ON

Discussion: HP-stress with higher VDS

• Fast dynamic RON ↑ only in 3 min with lower P-level• Again, very fast RON recovery down to ms range• HP-stress with VDS↑ promotes fast dynamic RON degradation

After 20 min HP-stress with VDS= 20 V, P≈ 12 W/mm

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10-710-610-510-410-310-210-1 100 101 102 103 1043

4

5

6

7

8

9

Time [sec]

RO

N [

-mm

]

Discussion:Different epi-supplier

RON_DC= 3.5 Ω∙mm

* Red solid line: same GaN-on-SiC HEMT design processed in the same lot on nominally identical epitaxial wafer from different epi-supplier (denoted by epi-supplier II)

RON_DC= 4.6 Ω∙mm

• Very different patterns of dynamic RON transient

virgin epi-supplier I

virgin epi-supplier IITransient from OFF (-5 V, 40 V) to ON

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Discussion: HP-stress on epi-supplier II

0.01

0.1

1

10

100

0

0.2

0.4

0.6

0.8

1

1.2

0 20 40 60 80 100 120

I GO

FF[m

A/m

m]

RO

N/R

ON(0

), I D

MAX

/I DM

AX(0

)

Time [min]

IDMAX

RON

IGOFF

• No prominent permanent degradation in RON, IDMAX and IGOFF

- Large increase of IGOFF recoverable

* HP-stress on epi-supplier II device: VDS= 20 V, ID≈ 0.6 A/mm, P≈ 12 W/mm

29

10-6 10-5 10-4 10-3 10-2 10-1 100 101 102 1030

2

4

6

8

10

12

Time [sec]

RO

N/R

ON

-DC

Discussion: Dynamic RON on epi-supplier II

2 hr HP-stress on epi-supplier II

Virgin epi-supplier II

• Minor increase in dynamic RON up to 2 hr HP-stress• Epi-supplier II device more robust than epi-supplier I

- RTH(thermal resistance) of epi-supplier II < RTH of epi-supplier I - Better heat dissipation through different buffer design

• Epi-supplier II wafer more traps than epi-supplier I


40 min HP-stress on epi-supplier I

30

Outline

1. Motivation



4. Discussion

5. Conclusion

31

Conclusion

• Developed new dynamic RON measurement methodology

• Key findings from HP electrical stress - Large increase in dynamic RON on a short-time scale - Formation of shallow traps most likely inside the AlGaN barrier or at its surface

• GaN HEMTs device operation under RF power or hard-switching conditions - Undesirable increase of dynamic RON on a very short time scale

impact of high-power stress on dynamic on-resistance of high-voltage gan hemts

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