impact of high-power stress on dynamic on-resistance of high-voltage gan hemts donghyun jin and...
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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
Motivation• Much less understanding
‒ Impact of electrical stress on dynamic RON
‒ 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
Motivation• Much less understanding
‒ Impact of electrical stress on dynamic RON
‒ Especially, high-power (HP) state in GaN device operation
Meneghesso et al, TED 2006
8
Motivation• Much less understanding
‒ Impact of electrical stress on dynamic RON
‒ Especially, high-power (HP) state in GaN device operation
• Goal‒ New methodology for dynamic RON measurement‒ Investigate the impact of high-power stress on dynamic RON
Meneghesso et al, TED 2006
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Outline
1. Motivation
2. Dynamic ON-resistance measurement
3. High-power stress experiment
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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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 )
• Dynamic RON measurement from pulsed-IV
VDS
ID
OFF (VGSQ, VDSQ)
ION @ VGS= 1 V 1/RON
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Dynamic RON measurement• New methodology for RON transient measurement
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
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0 1 2 3
x 10-3
0
0.02
0.04
0.06
0.08
Time [sec]
I D [
A/m
m]
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/m
m]
VDS
[V]0 1 2 3
x 10-3
0
0.02
0.04
0.06
0.08
Time [sec]
I D [
A/m
m]
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
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
102
103
104
3.5
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
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
102
103
104
3.5
4
4.5
5
5.5
Time [sec]
RO
N [
-mm
]
Dynamic RON measurement
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
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
102
103
104
3.5
4
4.5
5
5.5
Time [sec]
RO
N [
-mm
]
Dynamic RON measurement
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
OFF(-5 V, 40 V) to ON
18
Outline
1. Motivation
2. Dynamic ON-resistance measurement
3. High-power stress experiment
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
[mA
/mm
]
RO
N/R
ON(0
), I
DM
AX/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
103
0
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)
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HP-stress time
RON_DC increase
10 7%
20 8%
30 11%
40 16%
21
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
(ai)
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
103
0
2
4
6
8
10
12
Time [sec]
RO
N/R
ON
-DC
10-710
-610
-510
-410
-310
-210
-110
010
110
210
30
10
20
30
40
50
Time [sec]
RO
N [
-mm
]T= 25 C45
OFF(-10 V, 50 V) to ON
65
85105125150
T ↑
* tstress= 40 min sample
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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
103
0
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
* tstress= 40 min sample
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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 eV
0.75 eV0.57 eV
0.53 eV
0.45 eV
0.31 eV
0.23 eV
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Outline
1. Motivation
2. Dynamic ON-resistance measurement
3. High-power stress experiment
4. Discussion
5. Conclusion
26
10-6
10-5
10-4
10-3
10-2
10-1
100
101
102
103
1
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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10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
102
103
104
3
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 II
Transient 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
[mA
/mm
]
RO
N/R
ON(0
), I
DM
AX/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
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10-6
10-5
10-4
10-3
10-2
10-1
100
101
102
103
0
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
OFF(-10 V, 50 V) to ON
40 min HP-stress on epi-supplier I
30
Outline
1. Motivation
2. Dynamic ON-resistance measurement
3. High-power stress experiment
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