polarization super-junction - powdec powdec...conventional si-mos fet biasing n n g d s p p+ n + 9...
Post on 16-Aug-2021
9 Views
Preview:
TRANSCRIPT
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
Polarization Super-junction
A New Concept for
GaN High-Voltage Devices
1
H. Kawai
A. Nakajima
E. M. S. Narayanan
POWDEC K.K. The University of Sheffield (UoS), present : National Institute of Advanced Industrial Science and Technology (AIST)
The University of Sheffield (UoS)
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
2
1. About Powdec
2. Background
Issues for Today’s GaN Power Devices
3. Polarization Super-Junction, (PSJ) Concept
4. Application to Devices
5. Results and Discussion
6. Summary
-- Contents --
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
3
-- About POWDEC --
Established: May 2001
Location: Oyama-city, Japan
No. of employees: 20 Powdec core technology:
GaN growth using the original large scale MOCVD equipment
Power device development using unique growth techniques such as ELO (Epitaxial lateral overgrowth), PSJ (polarization super-junction)
Powdec is managed independently of its shareholders
to pursue its business interests
Mt. Fuji
150km
Narita 70
60
Fukushima 170km
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
4
-- Background--
Issues for Today’s GaN Power Devices
Reliability • Current Collapse
• Not high-breakdown voltage
• Avalanche resistance
• Life-time degradation
Cost • Substrate
• Thick buffer growth
• High cost front-end process
Need a new device approach
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
5
-- Background--
Current Collapse
Low drain bias
High drain bias
Drain Voltage, Vd
Dra
in C
urr
en
rt, I
d
Vg
Vg
Vd
VDD
Id R
0
Id
on
Vd
VDD
R
Time
Vg
On-state
off
Vstress
Off-state On-state
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
Decrease of electron
S G
D
AlGaN
GaN
S G
D
AlGaN
GaN
Ele
ctr
ic F
ield
Hot electrons captured in Deep traps Hot electrons captured in AlGaN Gate leakage Electrons captured
in the surface
Trapped electrons act as the negative bias under the channel
Increase in channel resistance
High field induces “Hot electrons”
Deep trap
Leakage
Channel electron
6
-- Background--
Origin of Current Collapse
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
SiN/SiO2 insulator
Source FP
Gate FP
Si substrate
AlN nucleation layer
AlGaN/AlGaN buffer
S G
AlGaN GaN
High quality passivation
D GaN-cap
Thick
7
-- Background--
High field limits GaN’s potential capability.
High field induces; Current collapse Low breakdown voltage Poor life time reliability
How to amend;
Lower the Field
Lower the gate leakage
Decrease the surface trap
Decrease the deep trap
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
S D
AlGaN
GaN
Field plate (FP)
G
Fie
ld (
E)
without FP
with FP
Split & decrease the field
8
-- Polarization Super-junction (PSJ) --
Traditional technology : Field plate (FP)
Max.Field(MV/cm)
On
-resis
tan
ce I
ncre
ase
(R
HV-R
LV)/
RLV [%
]
VDD=300V
(Toshiba semiconductor Company、SEMI FORUM JAPAN, power device seminar)
On-resistance increase vs. Peak field strength
Gate-edge
FP-edge
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
E
V
V
Deple-tion
n
n+
Conventional Si-MOS FET
biasing
n
n+
G
D
S
p
p+
n+
9
Super-junction (SJ) concept
Depleted whole
E
Flat distribution
n+
n
p p
biasing
Si Super-Junction-MOS FET
n+
-- Polarization Super-junction (PSJ) --
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
AlG
aN
u
-Ga
N
GaN
p-G
aN
potential
Polarization charge
Ev Ec
i-AlGaN
i-GaN hole
i-GaN ele.
Polarization charge
n+
p
p
n
GaN/AlGaN/GaN
GaN/AlGaN/GaN
Band structure
10
-- Polarization Super-junction (PSJ) --
GaN/AlGaN/GaN Polarization(PJ) structure acts similar to a silicon super-junction
n+
p
depleted
biasing
Super-junction Si-MOS FET
i-AlGaN
i-GaN
i-GaN
depleted
Polarization charge
biasing
Polarization charge
Ec Ev
AlG
aN
u
-GaN
GaN
p-G
aN
V
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
Existence of high density 2-dimensional hole gas (2DHG)
sapphire
buffer
i-GaN
i-Al.23Ga.77N
i-GaN
p+GaN
***nm
***nm
***nm
Layer structure
0
5
10
15
20
25
30
50 100 150 200 250 300
Ho
le D
en
sit
y (
1e1
2 /c
m2 )
Temperature ( K )
PJ
p-GaN
1.4E13 cm-2
Temperature dependence
of hole concentration
11
-- Polarization Super-junction (PSJ) --
PSJ
Freeze-out
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future F
ield
Flat distribution
12
-- Polarization Super-junction (PSJ) --
Application to lateral devices
S D
AlGaN
GaN
G B
PSJ region
Fie
ld
with FP
without FP
S D
AlGaN
GaN
Metal FP
G
Traditional metal field-plate Polarization super-junction
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
p-GaN G
i-GaN
Sapphire sub.
i-AlGaN
i-GaN
B
Lp:8mm
Lsd:22mm
Lgd:17mm
3mm
S D G
i-GaN
Sapphire sub.
i-AlGaN
Lsd:22 mm
Lgd:17 mm
S D
Lg:2 mm
PSJ-FET Reference HFET
13
-- Application to FET (PSJ-FET) --
• No passivation
• No field plate
• Gate-PSJ configuration
6mm 5mm Lg:2mm
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
Transfer Characteristics Off-state Characteristics
10-9
10-7
10-5
10-3
0 200 400 600 800D
rain
Cu
rre
nt
[A/m
m]
Drain Voltage [V]
Vg = -15 V
Super HFET
Reference
HFET
VB = 720 V
14
-- PSJ-FET; results --
Vth = ~5 V VB = ~720 V; ref-HFET < 200 V Leak current= ~sub mA/mm@700 V
0
0.1
0.2
0.3
0
20
40
60
-10 -8 -6 -4 -2 0 2
Dra
in C
urr
en
t [A
/mm
]
Gm
[m
S/m
m]
Gate Voltage [V]
Super HFET
Vd:10V
Vth:-4V
Id
GmGm
max:
55 mS/mm
PSJ-FET
PSJ-FET
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
Temperature dependence
PSJ-FET Reference HFET
0
0.1
0.2
0.3
0 5 10 15
Dra
in C
urr
en
t [A
/mm
]
Drain Voltage [V]
25
Reference HFET
150
Vg = 0 V
-2 V step℃
℃
Pinch-offed at 250 C
Id decreased due to phonon
scattering and band modulation Did not work at > 150 C
15
-- PSJ-FET; results --
0
0.1
0.2
0.3
0 5 10 15
Dra
in C
urr
en
t [A
/mm
]
Drain Voltage [V]
Vg = 0 V
250
-2 V step
25
Super HFET
℃
℃
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
PSJ-FET Reference HFET
~mA/mm leak current at 250 C
10-12
10-10
10-8
10-6
10-4
10-2
0 50 100 150 200
Dra
in C
urr
en
t [A
/mm
]
Drain Voltage [V]
Vg = -15 V
250
175
10025
Super HFET
℃
℃
℃
℃
10-12
10-10
10-8
10-6
10-4
10-2
0 50 100 150 200
Dra
in C
urr
en
t [A
/mm
]
Drain Voltage [V]
100
25
Reference HFET
150Vg = -15 V
℃
℃
℃
Exponential increase with temp.
16
Temperature dependence
at off-state condition
-- PSJ-FET; results --
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
Vd
Id
Vg=0V
Vd=+2V
measurement
Vg = -15 V
time
1 s
(20->350 V)
stress
transient
measure
17
Current collapse
Super HFET
Reference
HFET
1
2
3
4
5
6
0 100 200 300 400
Ro
nH
V / R
on
init
ial
Stress Voltage [V]
PSJ-FET
-- PSJ-FET; results --
Essentially no current collapse
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
0
50
100
150
200
250
300
350
400
450
-10 -8 -6 -4 -2 0 2
Id (
mA
/mm
)
Vgs (V)
Id saturate at Vg > -2 V VB > 830 V
18
B p-GaN
G
i-GaN
Sapphire sub.
i-AlGaN
i-GaN
Lg:2 mm
S D
Lgd=13mm
AlGaN
Source-PSJ configuration
Conv.
PSJ
Vds=10V
Vth=-4V
-10 -8 -6 -4 0 2 -2
450
400
350
300
250
200
150
100
50
0
Vgs (V)
-- PSJ-FET; results --
1.E-10
1.E-09
1.E-08
1.E-07
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
0
5
10
15
20
0 500 1000
Ig (A/m
m)
Id (
mA
/mm
)
Vds (V)
Conv. Super
Conv. (VB=130V)
Super (VB=830)
500 1000 0
20
15
10
5
0
1E-2
1E-3
1E-4
1E-5
1E-6
1E-7
1E-8
1E-9
1E-10
PSJ
PSJ Ig (
A/m
m)
Ig (
A/m
m)
Vds (V)
Id
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
Forward I-V
Vth:1.2 V
RonA : 1.3 mWcm2
Breakdown voltage > 1.1 kV
Reverse current : ~1 mA/mm
19
Schottky barrier diode
Reverse I-V
-- PSJ Applied to a Diode--
sapphire
i-GaN
i-AlGaN
P-GaN
12um A C
0
0.05
0.1
0.15
0.2
0 0.5 1 1.5 2 2.5 3 3.5
An
od
e C
urr
en
t [A
/mm
]
Anode Voltage [ V ]
W : 50 mm
Lac
: 12 mm RonA : 1.3 mWcm2
AlGaN/GaN SBD
PSJ-SBD
AlGaN SBD
10-9
10-8
10-7
10-6
10-5
10-4
10-3
10-2
-1200 -1000 -800 -600 -400 -200 0
An
od
e C
urr
en
t [A
/mm
]
Anode Voltage [ V ]
W : 50 mm
Lac
: 12 mm
VB > 1.1 kV
PJ-SBD
AlGaN/GaN SBD
VB = 400V
AlGaN SBD
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
20
-- Discussion --
Scalability of VB with PSJ length
Super-junction predicts the linear
increase of VB with the junction length
PSJ-length; Lp
sapphire
i-GaN
i-AlGaN
P-GaN
G PSJ length
D S
Fie
ld
V
Lp
Bre
akd
ow
n v
olt
ag
e (
VB
) ** MV/cm
Scalable with PSJ-length
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
sapphire
i-GaN
i-AlGaN
P-GaN
G PSJ length
D S Lp
21
-- Discussion --
Scalability of VB with PSJ length
Acknowledgement: High-voltage measurement was supported by “Agilent Technologies International Japan Ltd.”
0.01
0.1
1
10
100
0 1 2 3 4 5 6 7
Drain current at off-state vs. PSJ length
Dra
in C
urr
en
t [ u
A/m
m ]
Drain Voltage [ kV ]
Lp = 10 um
20 um30 um
40 um
Drain-current at off-state vs.
Drain-voltages
PSJ, Lp = 30um
S D
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
S D
22
-- Discussion --
Scalability of VB with PSJ length
0
2
4
6
8
10
0 10 20 30 40 50 60 70
VB vs, PSJ length
Bre
akd
ow
n V
olt
ag
e [
kV
]
PSJ length, Lp [ mm ]
line for
eye convenience
slope = 1.4 MV/cm
sapphire
i-GaN
i-AlGaN
P-GaN
G PSJ length
D S Lp
• VB increased linearly with PSJ length. • Breakdown field was about 1.4 MV/cm,
being smaller than 3.3 MV/cm.
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
23
-- Discussion --
0
5
10
15
20
25
0 5 10 15 20 25
Dra
in C
urr
en
t [ m
A/m
m ]
Drain voltage [ V ]
Lp = 40um
Vg = 0 V
-2 V
-4 V
-6 V
sapphire
i-GaN
i-AlGaN
D S Lp
5um 6um LSD
Lp = 10mm Lp = 40mm
0
10
20
30
40
50
60
0 2 4 6 8 10
Dra
in C
urr
en
t [ m
A/m
m ]
Drain Voltage [ V ]
Vg = 0 V
-2 V
-4 V
-6 V
Lp = 10um
slope
RonA=
22 mWcm2
RonA=
110 mWcm2
𝑳𝑺𝑫
𝒔𝒍𝒐𝒑𝒆 𝑽𝒈=𝟎 RonA ( mW cm2 ) =
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
24
-- Discussion --
Comparison of on-resistance
0.1
1
10
100
1000
0.1 1 10
Ro
nA
[ mW
cm
2 ]
Breakdown voltage, VB [ kV ]
Panasonic
('07)
Si-SJ MOSFET
SiC transistors
GaN-HFET
This work (PSJ-FET)
Si-SJ MOSFET
SiC transistors
GaN-HFET
This work (PSJ-FET)
Si-SJ MOSFET
SiC transistors
GaN-HFET
This work (PSJ-FET)
Toshiba
Fuji-Ele.
Infineon
Philips
Denso
Sanken('07)
Toshiba('07)
Furukawa
UCSB('06)
USCC('06)
AIST(SIT)
Kansai Ele.Pow.
(DMOS)
Rutgers Univ.(SIT)
Si-limit
6H-SiC-limit
4H-SiC-limit
GaN-limit
SiCED
Cree(DMOS)
Rutgers Univ.(SIT)
PSJ-Diode
1mm
Panasonic 10kV GaN-HFET
sapphire
i-GaN
i-AlGaN
D S Lp
POWDEC 6kV PSJ-FET
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
25
-- Summary --
We proposed a new method to realize GaN
transistors and diodes enabling high-VB and
negligible current collapse.
Polarization super-junction (PSJ)
i-AlGaN
i-GaN
hole
i-GaN
electron Polarization
charge
Which consists of basically
GaN/AlGAN/GaN double hetero-
junction in which 2DHG and 2DEG
co-exist.
The PSJ system acts similar to a
silicon super-junction
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
26
substrate
AlN
Thick buffer layer
S G
AlGaN GaN
D GaN-cap
-- Summary --
As a consequence,
the PSJ system can eliminate the barriers
encountered in the present metal field-plate
based device system.
• Breakdown voltage
• Current collapse
• Process cost
• Epi-cost
• etc.
G S D
AlGaN GaN
p-GaN
AlN nucleation layer
B
composite substrate
IWWPE2012, 2-nd April 2012, Hsinchu, Taiwan . POWDEC K.K.
GaN for Green Future
27
Thank you very much
for your careful attention!!
GaN for Green Future
top related