Transcript No Slide Title

ZnO PN Junctions for Highly-Efficient, Low-Cost Light
Emitting Diodes
David P. Norton, P.I.
Materials Science and Engr.
University of Florida
Fan Ren
Chemical Engr.
University of Florida
Stephen Pearton
Materials Science and Engr.
University of Florida
Prime Recipient: University of Florida
Work Performed Under Agreement:
DE-FC26-04NT42271
U. S. Department of Energy
National Energy Technology Laboratory
COR: Ryan Egidi
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
Project Objectives
• Develop solid state lighting technology based on wide bandgap
ZnO light emitting diodes (LED)
– Achieve high p-type carrier concentrations in epitaxial (Zn,Mg)O thin films
– Realize band edge emission from a ZnO-based pn homojunction
– Achieve band edge emission for ZnO-based pn heterojunctions that are
designed to yield efficient light emission.
– Related objectives
• Understand the doping behavior of phosphors and nitrogen in ZnO and ZnMgO
• Identify the potential and limitations of ZnO pn junction LED performance
• Achieve electroluminescence in polycrystalline ZnO-based pn junctions
fabricated on glass.
Ohmic ring
n-ZnMgO p-ZnMgO
Ohmic ring
c
p-ZnO
p-ZnMgO
ZnO
n-ZnMgO
n+-ZnO
a
substrate
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
ħω
ZnO
Expected Benefits
• Enhanced Performance in LEDs
– Light-emitting diode technologies are the most attractive
approach to energy-efficient solid state lighting
– ZnO appears equivalent to the nitrides ( leading material
candidate) for all relevant optical properties and has an
exciton state that is significantly more stable at room
temperature holds significant potential to outperform the
nitride devices
ZnO
• Reduction in Cost
– ZnO-based devices have been realized using thin films
deposited at temperatures on the order of 400-600˚C,
which is significantly lower that that for the nitrides.
Reduced temperature alone should lead to lower
manufacturing costs.
– Functional ZnO electronic devices can be fabricated on
inexpensive substrates, such as glass. For the large-area
photonic application of solid state lighting,
polycrystalline ZnO LED’s would present a remarkable
opportunity for technology.
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
GaN
Bandgap (eV) 3.44
µe (cm2/V-sec) 220
µh (cm2/V-sec) 10
me
0.27mo
mh
0.8mo
exciton binding 28
energy (meV)
ZnO
3.2
200
5-50
0.24mo
0.59mo
60!!
Budget Period
BP#1
Recipient
BP#2
BP#3
Total
Gov.
Funding
Cost
Share
Gov.
Funding
Cost
Share
Gov.
Funding
Cost
Share
Gov.
Funding
$315,167
$78,792
$302,128
$75,532
$297,242
$74,310
$914,537
CS %:
20%
20%
October
27,128
November
25,000
December
25,000
January
25,000
February
25,000
March
25,000
April
25,000
May
25,000
June
25,000
July
25,000
August
25,000
September
25,000
302,128
Cost
Share
$228,634
20%
20%
BP#3 – Oct. 2006 –
Sept. 2007 (estimated)
BP#2– Oct. 2005 – Oct.
2006 (estimated)
total
Project Funding Profile
Total costs 10/01/05-9/30/05
$302,128
Total costs 10/01/06-9/30/07
$297,242
October
24,000
November
24,000
December
24,000
January
24,000
February
24,000
March
24,000
April
24,000
May
24,000
June
24,000
July
24,000
August
27,000
September
30,242
total
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
297,242
Project Status (Budget Period 2)
ZnO-based pn junctions for light emitting diodes
Three pertinent issues
– Achieve high p-type carrier
concentrations in epitaxial and
polycrystalline films
Materials issue
contact
contact
p-type ZnO
n-type ZnO
– Realizing band edge emission
from pn homojunctions
Proof of concept
SUBSTRATE
Ohmic ring
n-ZnMgO p-ZnMgO
– Investigating pn heterojunction
constructs that should yield
efficient light emission.
Device Development
Ohmic ring
p-ZnO
p-ZnMgO
ZnO
n-ZnMgO
n+-ZnO
Glass substrate
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
ħω
ZnO
Research task with milestones in Budget Period 2
Project Status (Budget Period 2)
Title
Metric/Method of Verification
Projected date for
milestone
completion
(month/year)
Growth of p-type (Zn,Mg)O films
Achieve 10E17 cm-3 p-type carrier density in ZnO film
7/06
Formation of pn homojunction thin film
structure
Optimize crystalline/polycrystalline pn junction structure film
growth process with respect to IV
1/06
Fabrication of pn homojunction device
Achieve UV light emission from pn homojunction device
4/06
Characterization of pn homojunction
Determine efficacy of pn homojunction for LED
7/06
Growth of p-(Zn,Mg)O/ZnO/n-(Zn,Mg)O
pn heterostructure
Optimization of epitaxial heterostructure thin film junction
7/06
Fabrication of p-(Zn,Mg)O/ZnO/n(Zn,Mg)O pn heterojunction devices
Achieve nonlinear rectifying IV in pn heterojunction device
7/06
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
Research task: Achieve 1017 cm-3 p-type carrier density in
ZnO film
Reproducibility of p-type ZnO growth
RTA annealing study
- Structure
② Post-annealing for 1 hour (150mTorr)
800 ℃
③ ZnO:P growth for 3 hours
ZnO :P0.005
Undoped buffer
Sapphire
400 ℃
A) Temperature effects
(Fixed pressure : 150mTorr)
B) Pressure effects
(Fixed temperature 700 ℃)
① Buffer : 20 mTorr for 1 hour
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
: n-type
(ZnO:P0.005) - Hall data (150 mTorr growth pressure)
Growth
Temp
(℃)
As grown
850
3 min
950
2 min
3 min
1 min
2 min
3 min
4400 Ω-cm
140 Ω-cm
9.0 Ω-cm
1.1 Ω-cm
0.76 Ω-cm
3.9E+16cm-3
2.3E+15cm-3
1.2E+17cm-3
1.8E+18cm-3
4.9E+18cm-3
5.4E+18cm-3
0.037cm2/Vs
0.63cm2/Vs
0.37cm2/Vs
0.38cm2/Vs
1.2cm2/Vs
1.5cm2/Vs
1700 Ω-cm
490 Ω-cm
70 Ω-cm
5.0 Ω-cm
6.3 Ω-cm
11 Ω-cm
2.9E+15cm-3
1.2E+16cm-3
4.3E+17cm-3
3.0E+18cm-3
2.7E+18cm-3
2.0E+19cm-3
1.3cm2/Vs
1.0cm2/Vs
0.20cm2/Vs
0.41cm2/Vs
0.36cm2/Vs
0.028cm2/Vs
480 Ω-cm
3400 Ω-cm
1700 Ω-cm
360 Ω-cm
24Ω-cm
19 Ω-cm
39 Ω-cm
1.4E+16cm-3
3.9E+15cm-3
8.8E+15cm-3
4.2E+16cm-3
4.6E+17cm-3
5E+17cm-3
4.1E+17cm-3
2.4E+17cm-3
0.98cm2/Vs
0.47cm2/Vs
0.40cm2/Vs
0.40cm2/Vs
0.56cm2/Vs
0.71cm2/Vs
0.80cm2/Vs
0.66cm2/Vs
2.2 Ω-cm
630 Ω-cm
900 Ω-cm
140 Ω-cm
4.8 Ω-cm
21 Ω-cm
65 Ω-cm
4.8E+17cm-3
1.4E+16cm-3
1.0E+16cm-3
2.2E+17cm-3
1.1E+18cm-3
4E+17cm-3
9.5E+17cm-3
1.0E+18cm-3
5.8cm2/Vs
0.68cm2/Vs
0.67cm2/Vs
0.21cm2/Vs
1.1cm2/Vs
2.4cm2/Vs
0.30cm2/Vs
0.094cm2/Vs
2.0 Ω-cm
360 Ω-cm
1400 Ω-cm
100 Ω-cm
4.9 Ω-cm
17 Ω-cm
4.5 Ω-cm
15 Ω-cm
4.5E+17cm-3
2.6E+16cm-3
5.1cm-3
2.6E+16cm-3
3.6E+18cm-3
2E+18cm-3
3.7E+18cm-3
2.0E+17cm-3
7.1cm2/Vs
0.66cm2/Vs
0.91cm2/Vs
2.4cm2/Vs
0.36cm2/Vs
0.15cm2/Vs
0.38cm2/Vs
2.2cm2/Vs
650
800
900
4400 Ω-cm
600
750
: p-type
RTA temperature (℃) / time (min)
2 min
700
: p or n-type
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
17 Ω-cm
7.1 Ω-cm
: n-type
( ZnO:P0.005 ) – Hall data (700°C growth temperature)
P(O2)
(m Torr)
100
As grown
850
10
1
900
3 min
1 min
2 min
950
3 min
1 min
3 min
19 Ω-cm
39 Ω-cm
3400
1700 Ω-cm
360 Ω-cm
24 Ω-cm
1E+16cm-3
4E+15cm-3
9E+15cm-3
4E+16cm-3
4E+17cm-3
5E+17cm-3
4E+17cm-3
2E+17cm-3
0.98cm2/Vs
0.47cm2/Vs
0.40cm2/Vs
0.40cm2/Vs
0.56cm2/Vs
0.71cm2/Vs
0.90cm2/Vs
0.68cm2/Vs
76 Ω-cm
34 Ω-cm
38 Ω-cm
36 Ω-cm
5.5 Ω-cm
2E+19cm-3
-
17 Ω-cm
2 min
480 Ω-cm
0.07cm2/Vs
50
: p-type
RTA temperature (℃) / time (min)
2 min
150
: p or n-type
9400Ω-cm
20 Ω-cm
33 Ω-cm
6E+13cm-3
7E+17cm-3
2E+17cm-3
1E+18cm-3
4E+16cm-3
1E+18cm-3
2E+18cm-3
10cm2/Vs
0.44cm2/Vs
0.39cm2/Vs
0.14cm2/Vs
5.3cm2/Vs
0.11cm2/Vs
0.08cm2/Vs
1.1 Ω-cm
8E+4Ω-cm
4E+4Ω-cm
170 Ω-cm
280 Ω-cm
4.7E6Ω-cm
33 Ω-cm
8.4 Ω-cm
28 Ω-cm
8E+18cm-3
5E+13cm-3
4E+13cm-3
1E+16cm-3
9E+16cm-3
1E+12cm-3
2E+17cm-3
4E+18cm-3
4E+19cm-3
0.65cm2/Vs
1.6cm2/Vs
4.3cm2/Vs
3.4cm2/Vs
0.24cm2/Vs
1.1cm2/Vs
0.94cm2/Vs
0.20cm2/Vs
0.005cm2/Vs
1.4 Ω-cm
9400 Ω-cm
3100 Ω-cm
27 Ω-cm
5700 Ω-cm
51 Ω-cm
45 Ω-cm
25 Ω-cm
58 Ω-cm
4E+18cm-3
4E+16cm-3
5E+15cm-3
9E+16cm-3
4E+16cm-3
9E+18cm-3
6E+16cm-3
1E+19cm-3
3E+18cm-3
1.3cm2/Vs
0.02cm2/Vs
0.44cm2/Vs
2.6cm2/Vs
0.03cm2/Vs
0.01cm2/Vs
2.5cm2/Vs
0.02cm2/Vs
0.04cm2/Vs
0.75 Ω-cm
1000Ω-cm
840 Ω-cm
3.3 Ω-cm
7.6 Ω-cm
220 Ω-cm
2.3 Ω-cm
2.9 Ω-cm
4.6 Ω-cm
9E+18cm-3
2E+17cm-3
4E+17cm-3
3E+18cm-3
3E+18cm-3
9E+16cm-3
3E+18cm-3
5E+18cm-3
4E+18cm-3
0.90cm2/Vs
0.03cm2/Vs
0.02cm2/Vs
0.61cm2/Vs
0.28cm2/Vs
0.33cm2/Vs
0.89cm2/Vs
0.43cm2/Vs
0.33cm2/Vs
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
p=1016cm-3
2. Zn0.95Mg0.05O:P0.02 (Hall data)
RTA temperature (℃)
Growth
Temperature
(℃)
550
(ZMP-13)
600
(ZMP-14)
650
(ZMP-15)
650
(ZMP-16)
As grown
600
700
800
900
4.98E+16
2.70E+17
3.67E+16
5.20E+14
1.03E+17
(M) 0.14546
(M) 0.085742
(M) 0.25074
(M) 1.2396
(M) 0.14526
(R) 860.87
(R) 269.23
(R) 678.83
(R) 9591.4
(R) 419.61
7.18E+16
1.54E+17
7.06E+16
1.59E+16
2.89E+17
(M) 1.4197
(M) 0.37251
(M) 0.37137
(M) 0.40281
(M) 0.58556
(R) 61.309
(R) 108.86
(R) 238.78
(R) 962.38
(R) 36.798
4.92E+13
9.34E+17
4.50E+13
9.44E+13
6.16E+17
(M) 0.12126
(M) 0.5125
(M) 2.3158
(M) 0.82754
(M) 0.52519
(R) 1.09E+6
(R) 12903
(R) 60500
(R) 78126
(R) 19.321
3.49E+18
3.90E+18
3.45E+18
2.53E+17
1.38E+17
(M) 34.55
(M) 34.913
(M) 33.670
(M) 3.0596
(M) 5.33
(R) 0.051714
(R) 0.045842
(R) 0.053734
(R) 8.0610
(R) 8.47
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
1. Zn0.9Mg0.1O:P0.02 (Hall)
p=1-6x1015 cm-3
RTA temperature
Thickness of
buffer layer
(nm)
< 500 ℃ >
Growth
Temperature
< 200 nm >
As grown
600
700
800
30
( ZMP-1 )
3.6735E14
(M) 0.5361
(R) 32457
2.5582E+15
0.7151
3394.2
1.6799E+16
0.40346
925.05
6.3720E+14
0.60931
16061
100
( ZMP-2 )
2.6561E14
(M) 0.4735
(R)49655
2.1134E+15
0.25347
11652
2.8783E+15
0.34103
6357.1
4.1998E+14
0.26480
57642
200
( ZMP-3 )
2.8614E15
(M) 0.1893
(R) 11516
2.7098E+14
0.45735
50565
1.0210E+14
0.50579
12131
Semi-insulating
400
( ZMP-4 )
7.4256E17
(M) 4.5337
(R) 1.855
1.0167E+15
0.93540
6551.3
2.9490e+14
1.0129
20883
Semi-insulating
550 ℃
( ZMP-10 )
6.8235E+15
(M) 1.2349
(R) 732.49
4.56E+16
(M) 0.11955
(R) 1140.1
7.72E+16
(M) 0.1129
(R) 720.15
600 ℃
( ZMP-5 )
7.784E+17
(M) 0.1382
(R) 57.388
1.7995E+15
0.42028
8214.4
3.5071E+14
0.49244
36207
600 ℃
( ZMP-11 )
1.1999E+13
(M) 56.677
(R) 8932.8
5.58E+15
(M) 0.12621
(R) 8909.4
8.24E+14
(M) 0.21207
(R) 35716
650 ℃
( ZMP-12 )
4.2397E+16
(M) 0.39604
(R) 371.64
6.95E+16
(M) 0.07554
(R) 1198.4
700 ℃
(ZMP-6)
1.499E+17
(M) 1.1119
(R) 37.421
800 ℃
(ZMP-7)
900 ℃
(ZMP-8)
850
900
925
975
4.27E+14
(M) 18.25
(R) 788
1.29E+17
0.0549
875.03
6.36E+16
6.31E+17
(M) 2.6358
(M) 7.9413
(R) 37.15
(R) 1.2466
Semi-insulating
Semi-insulating
(875 ℃)
1.0427E+12
4.35E+17
(M) 139.02
(M) 1.4595
(R) 46452
(R) 9.8393
1.64E+17
(M) 0.058
(R) 657
1.68E+16
4.28E+17
(M) 0.24019
(M) 1.9607
(R) 1564.7
(R) 7.4443
7.115E+16
0.411
212.46
4.21E+16
0.2797
531.03
1.095E+15
1.1135
5094.7
6.4643E+16
0.52519
183.36
4.67E+18
(M) 39.436
(R) 0.033875
3.36E+18
40.78
0.0455
3.44E+15
11.748
156.65
2.824E+14
100.66
218.98
6.7577E+16
1.3676
67.410
1.368E+19
(M) 33.410
(R) 0.013655
1.4026E+19
27.567
0.016144
1.4829E+19
2.3144
0.18208
7.0575E+17
0.90632
9.7647
3.8507E+17
1.8439
8.7689
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
High-quality undoped ZnO epitaxial films realized by PLD
◈ Growth conditions
Undoped ZnO
( ~ 1um)
Buffer layer (25nm)
Sapphire Substrate
▶ Bulk layer growth
- Target : undoped ZnO
- Tg : 650 ℃
- Pressure : 10 mTorr ( O2 + O3 mixture gas )
- Laser : 180 mJ / 4 Hz
- Ablation time : 2 hrs 20 min ( 1.22 Å / s )
▶ Buffer layer growth
- Target : undoped ZnO
- Pressure : 1m Torr ( O2 + O3 mixture gas )
- Tg : 850 ℃
- Laser : 180 mJ / 1 Hz
- Ablation time : 9 min ( 0.53 Å / s )
Narrow Omega Rocking Curve
◈ Hall data
n = 2.4E+16 ( /cm3 )
µ = 87.7 ( cm2/V•s )
ρ = 3.1 ( ohm•cm )
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
( rms : 1.557 nm)
Research task: Determine efficacy of pn homojunction for LED
p-n homojunctions in n-ZnO bulk single crystals by diffusion
from a Zn3P2 source
• p-n junctions have been formed in lightly n-type (1017 cm-3)
bulk, single-crystal ZnO substrates by diffusion of P from a
Zn3P2 dopant source in a closed-ampoule system.
4
Current(mA)
3
/ZnO pn diode
2
1
0
-6
-4
-2
0
2
4
6
Voltage (V)
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
Research task: Achieve UV light emission from pn homojunction
device
Electroluminescence From N+-Implanted Bulk ZnO
•
Band-Edge Electroluminescence From N+-Implanted Bulk ZnO
– Studies of phosphorus and nitrogen doping via ion implantation
carried out.
– Rectifying junctions and light emission realized. N+ ion implantation
at moderate doses (1012-1013 cm-2) into nominally undoped (n~1017
cm-3) bulk single-crystal ZnO substrates followed by annealing in the
range 600-950°C was used to fabricate diodes that show band-edge
electroluminescence at 120K (~390 nm) under forward bias
conditions.
0.04
+
Current(A)
0.03 N implanted ZnO
0.02
0.01
Au (80nm)
Ni (20nm)
600C, O2, 2 mins.
800C, O2, 2 mins.
950C, O2, 2 mins.
hυ
N+ implanted ZnO (300nm)
0.00
ZnO substrate
-0.01
Ti (20nm)
-0.02
Au (200nm)
-0.03
-0.04
-15
-10
-5
0
5
10
15
Voltage(V)
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
N-implanted ZnO crystals:
Light Intensity Performance
Onset > 8 volts
Devices
600C
RTA
800C
RTA
950C
RTA
P at 100mA
(Lumen)
3.57×10-9
8.5×10-10
0
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
Si diode test
15
8.0x10
-8
6.0x10
-8
4.0x10
-8
2.0x10
-8
15
8.0x10
-8
6.0x10
-8
4.0x10
-8
2.0x10
-8
15
8.0x10
-8
6.0x10
-8
4.0x10
-8
2.0x10
-8
0
0.00
0.0
0.02
+
5
N -ZnO(3-2)
700C for 180s
900C for 10s
Voltage
Power
0
0.00
0.04
Voltage (V)
5
Voltage (V)
N -ZnO(3-2)
500C for 180s
900C for 10s
Voltage
Power
10
10
5
0
0.00
0.0
0.02
Current (A)
0.04
0.0
0.02
Current (A)
15
8.0x10
Current (A)
15
-8
0.04
8.0x10
-8
6.0x10
-8
4.0x10
-8
2.0x10
-8
4.0x10
-8
2.0x10
-8
10
+
N -ZnO(3-2)
500C for 10mins
900C for 10s
Voltage
Power
5
0
0.00
0.0
0.02
0.04
0.06
0.08
0.10
Current (A)
Voltage (V)
-8
10
5
0
0.00
0.0
0.02
0.04
0.06
Current (A)
Light emission for diodes with onset>5 volts
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
0.08
0.10
Power(mW)
6.0x10
Power(mW)
Voltage (V)
+
N -ZnO(3-2)
500C for 180s
950C for 10s
Voltage
Power
Power(mW)
+
Power(mW)
10
Power(mW)
Voltage (V)
+
N -ZnO(3-2)
500C for 180s
1000C for 10s
Voltage
Power
400 450 500 550 600 650 700
Wavelength(nm)
• Attribute optical emission to high-field
carrier injection
• Current focus is on pn junction
heterostructure devices for minority carrier
injection LED
– Epitaxial ZnMgO doped with P or N
• High hole concentration
– Formation of heterojunction device
• Minority carrier injection
PL intensity (arb. unit)
N+ implanted ZnO
900C O2 300mTorr 45mins
100 mA
30 mA
10 mA
device off
T= 298 K
400000
350000
Un-implanted ZnO
Implanted ZnO
300000
250000
200000
150000
100000
50000
0
EL intensity (arb. unit)
EL intensity(arb. unit)
16000
14000
12000
10000
8000
6000
4000
2000
0
12000
I= 30 mA
10000
T= 120 K
T= 298 K
8000
6000
4000
2000
0
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
400
450
500
550
wavelength (nm)
600
Vertical ZnO NWs/PEDOT LED
Nanowire Array
The cross section schematic of ZnO nanowires LED
1.00x10
I-V curve
L-I Curve
(378)
1.2
6
PL at RT
-8
Voltage (V)
1.0
0.8
0.6
0.4
7.50x10
4
-8
5.00x10
2
0.2
0.0
-8
2.50x10
0
350
400
450 500 550 600
Wavelength ( nm )
650
700
0.000
0.005
0.010
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
0.015
Current (A)
0.020
0.025
Light intensity (mW)
PL Intensity ( a. u. )
-7
8
1.4
Efforts toward epitaxial light-emitting homojunction
and/or heterojuction
• Multiple devices fabricated and tested
–
–
–
–
ZnO:P/ZnO:Ga/ZnO buffer/Al2O3
ZnO:P/ZnO:Ga/ZnO buffer/ZnO single crystal
ZnMgO:P/ZnO:Ga/ZnO buffer/Al2O3
ZnO:As/ZnO:Ga/ZnObuffer/Al2O3
• High leakage currents (non-rectifying I-V) observed as persistent
limitation
– Possible origins of leakage currents
• Leakage paths along ZnO surface due to processing-induced surface
conduction
• P-type to n-type conversion of P-doped ZnO due to processing
• Pinholes in p-type layer due to surface roughness
• Efforts in Budget Period 3 will focus on identifying and eliminating
cause(s) of leakage currents
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
3. ZnO:P0.01 ( PL of p-type samples )
Band edge PL and p-type seen in P-doped ZnO!
① ZP-4(950) (Tg = 600℃)
② ZP-6(900) (Tg = 700℃)
50000
30000
25000
Intensity (a.u.)
Intensity (a.u.)
40000
30000
20000
10000
20000
15000
10000
5000
0
0
350
400
450
500
550
600
650
350
700
400
450
500
550
600
650
700
Wavelength (nm)
Wavelength (nm)
/ cm3
Ohm-cm
Cm2/v-s
RTA
/ cm3
Ohm-cm
Cm2/v-s
RTA
1.61E+17
77.67
0.4998
950 ℃
1.55E+17
48.827
0.8139
900 ℃
④ ZP-7(900) (Tg = 800℃)
35000
35000
30000
30000
25000
25000
Intensity (a.u.)
Intensity (a.u.)
③ ZP-6(950) (Tg = 700℃)
20000
15000
10000
5000
20000
15000
10000
5000
0
0
350
400
450
500
550
600
650
700
350
400
Wavelength (nm)
450
500
550
600
650
700
Wavelength (nm)
/ cm3
Ohm-cm
Cm2/v-s
RTA
/ cm3
Ohm-cm
Cm2/v-s
RTA
2.37E+15
801.36
3.2161
950 ℃
1.98E+17
46.57
0.67867
900 ℃
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
◈ Zn0.9Mg0.1O:P0.02 ( PL of p-type samples )
① ZMP-3 (Tg = 500℃)
② ZMP-5 (Tg = 600℃) : Not reproducible
12000
30000
10000
25000
8000
20000
③ ZMP-10 (Tg = 550℃)
20000
6000
4000
Intensity (a.u.)
Intensity (a.u.)
Intensity (a.u.)
15000
15000
10000
2000
5000
0
0
10000
5000
0
350
400
450
500
550
600
650
700
350
400
450
Wavelength (nm)
500
550
600
650
350
700
400
450
500
550
600
650
700
Wavelength (nm)
Wavelength (nm)
/ cm3
Ohm-cm
Cm2/v-s
RTA
/ cm3
Ohm-cm
Cm2/v-s
RTA
/ cm3
Ohm-cm
Cm2/v-s
RTA
2.86E+15
11516
0.1893
as grown
7.78E+17
57.388
0.1382
as grown
6.82E+15
732.49
1.2349
as grown
④ ZMP-3(700) (Tg = 500℃)
⑤ ZMP-6(800) (Tg = 700℃)
No evidence for band
edge PL in ZnMgO:P
films
80000
250000
70000
200000
Intensity (a.u.)
Intensity (a.u.)
60000
50000
40000
30000
20000
150000
100000
50000
10000
0
0
350
400
450
500
550
600
650
350
700
400
450
500
550
600
650
700
Wavelength (nm)
Wavelength (nm)
/ cm3
Ohm-cm
Cm2/v-s
RTA
/ cm3
Ohm-cm
Cm2/v-s
RTA
1.02E+14
12134
0.50579
700 ℃
1.10E+15
5094.7
1.1135
800 ℃
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
Candidate “i” layer for p-i-n LED
① Good PL(small deep level) + low carrier density
Intensity (a.u.)
0.12
0.10
0.08
0.06
0.04
350
400
450
500
550
600
650
700
Wavelength (nm)
< PL >
< XRD rocking curve > : FWHM = 0.229 °
< Hall > : 1.07E+17 /cm3 , 36.44 cm2/v-s , 1.65 ohm-cm
• Growth condition :
- Substrate : sapphire c-plane
- Target : undoped ZnO
- Laser : 350 mJ / 1Hz
- Working pressure (O2 + O3 ) : 30 mTorr
- Ablation time : 2 hr
- Growth temperature : 800℃
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
MgO buffer: lowers background carrier density by factor of 5
② The lowest carrier density ( Still working ) – not completed
< structure >
< Hall > : 1.99+16 /cm3 , 22.30 cm2/v-s , 15.75 ohm-cm
< PL >
0.05
ZnO epi-layer (0.4㎛)
MgO buffer layer (~50nm)
Sapphire c-plane
Intensity (a.u.)
0.04
0.03
0.02
0.01
0.00
350
400
450
500
550
600
650
700
Wavelength (nm)
• Growth condition :
- Substrate : sapphire c-plane
- Target : undoped ZnO
- Laser : 350 mJ / 1Hz
- Working pressure (O2 + O3 ) : 30 mTorr
- Ablation time : 2 hr
- Growth temperature : 800℃
( buffer layer : MgO at 450 ℃, P : 10-4, time : 1 hr , 350 mJ/ 1Hz )
( At many other conditions, the carrier density also shows low 16 )
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
1. Growth condition
1. Buffer layer
2. Epi-layer
- Laser : 350 mJ / 1Hz
- Laser : 350 mJ / 1Hz
- Pressure (O2 + O3 ) : 30 mTorr
- Temperature : 500 ℃
ZnO epi-layer (0.4㎛)
- Pressure (O2 + O3 ) : 30 mTorr
ZnO buffer layer
- Ablation time : 2 hr
Sapphire c-plane
- Temperature : 800 ℃
- Ablation time : 2 hr
① 50 nm
② 100 nm
③ 200 nm
④ 300 nm
Epi-layer
500 ℃
Buffer
Conditions for next slide
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
800 ℃
Low temp growth of ZnO buffer yields low mobility in undoped ZnO films
3. Hall
2.50E+017
1.2
1.0
Mobility (cm /v-s)
3
Carrier density (1/cm )
2.00E+017
0.8
2
1.50E+017
1.00E+017
5.00E+016
0.6
0.4
0.2
0.0
0.00E+000
50
100
150
200
250
300
50
Thickness of buffer layer (nm)
100
150
200
250
300
Thickness of buffer layer (nm)
3000
Thickness of
buffer layer
(nm)
Concentration
(/cm3)
Mobility
(cm2/v•s)
Resistivity
(ohm•cm)
2000
50
4.35E+16
1.1
130.70
1500
100
5.12E+16
0.523
233.64
200
2.88E+16
0.0824
2642.5
300
2.16E+17
0.0414
700.24
As grown
1.07E+17
36.44
1.65
MgO (~50nm)
1.99E+16
22.30
15.75
Resistivity (ohm-cm)
2500
1000
500
0
50
100
150
200
250
300
Thickness of buffer layer (nm)
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
◈ Growth conditions
▶ Bulk layer growth
- Target : undoped ZnO
Undoped ZnO
( ~ 1um)
- Tg : 850 ℃
- Pressure : 10 mTorr ( O2 + O3 mixture gas )
- Laser : 180 mJ / 4 Hz
Buffer layer (25nm)
Sapphire Substrate
- Ablation time : 2 hrs 2 min ( 1.22 Å / s )
▶ Buffer layer growth
- Target : undoped ZnO
- Tg : 850 ℃
-Pressure ( O2 + O3 mixture gas )
① without buffer
● Characterization
- XRD rocking curve
- AFM
- SEM
- Optical microscopic
- Hall
- Thickness
② 0.01 mTorr
③ 0.1 mTorr
④ 1 mTorr
⑤10 mTorr
- Laser : 180 mJ / 1 Hz
- Ablation time : 9 min ( 0.53 Å / s )
Conditions for next slide
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
◈ Hall
① Resistivity
② Carrier density
0.055
2.80E+018
0.050
Resistivity (ohm-cm)
3
Carrier density (1/cm )
2.60E+018
0.045
0.040
0.035
0.030
2.20E+018
2.00E+018
1.80E+018
1.60E+018
0.025
0.1
1
Without buffer 0.01
Working pressure of buffer layer (mTorr)
2.40E+018
10
Without buffer 0.01
0.1
1
10
Working pressure of buffer layer (mTorr)
Excellent mobility for ZnO films!!!
③ Mobility
90
88
84
2
Mobility (cm /v-s)
86
82
80
78
76
74
72
Without buffer 0.01
0.1
1
10
Working pressure of buffer layer (mTorr)
Working pressure
of
buffer layer
(mTorr)
Concentration
(/cm3)
Mobility
(cm2/v•s)
Resistivity
(ohm•cm)
Without buffer
1.6495E18
73.61
0.05146
0.01
2.7502E18
85.476
0.02661
0.1
2.3765E18
87.606
0.03001
1
2.2949E18
85.443
0.03187
10
1.8874E18
87.371
0.03803
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
◈ FWHM of XRD rocking curve
Low temperature nucleation yields poorer crystallinity
Growth temperature of
Omega rocking
the buffer layer (℃)
FWHM (arcsec)
250
450
242.64
(0.0674°)
550
210.96
(0.0586°)
650
206.64
(0.0574°)
750
49.32
(0.0137°)
850
47.16
(0.0131°)
FWHM (arcsec)
200
150
100
50
500
600
700
800
o
Buffer growth temperature ( C)
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
◈ Hall
① Resistivity
② Carrier density
0.11
2.40E+018
2.20E+018
3
Carrier density (1/cm )
Resistivity (ohm-cm)
0.10
0.09
0.08
0.07
0.06
0.05
2.00E+018
1.80E+018
1.60E+018
1.40E+018
1.20E+018
1.00E+018
0.04
8.00E+017
0.03
6.00E+017
500
600
700
500
800
600
700
800
o
Buffer growth temperature ( C )
o
Buffer growth temperature ( C )
Low temperature nucleation yields low mobility
③ Mobility
85
Growth temperature
of buffer layer (℃)
Concentration
(/cm3)
Mobility
(cm2/v•s)
Resistivity
(ohm•cm)
450
1.9011E+18
65.672
0.050127
550
7.4896E+17
83.349
0.10035
650
1.7959E+18
73.508
0.0437381
750
8.5180E+17
78.111
0.084127
850
2.2949E18
85.443
0.03187
2
Mobility (cm /v-s)
80
75
70
65
500
600
700
800
o
Buffer growth temperature ( C )
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
Optimized thick undoped ZnO films
◈ Growth conditions
▶ Bulk layer growth
- Target : undoped ZnO
Undoped ZnO
( ~ 1um)
- Tg
: 650 ℃
- Pressure : 10 mTorr ( O2 + O3 mixture gas )
- Laser : 180 mJ / 4 Hz
- Ablation time : 2 hrs 20 min ( 1.22 Å / s )
Buffer layer (25nm)
Sapphire Substrate
▶ Buffer layer growth
- Target : undoped ZnO
- Pressure : 1m Torr ( O2 + O3 mixture gas )
- Tg : 850 ℃
Conditions for next 2 slides
- Laser : 180 mJ / 1 Hz
- Ablation time : 9 min ( 0.53 Å / s )
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
◈ AFM
( rms : 3.323 nm)
① 10 by 10 ㎛
50 nm
② 5 by 5 ㎛
( rms : 1.557 nm)
30 nm
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
◈ Omega Rocking Curve
◈ Hall data
: 2.3971E+16 ( /cm3 ) , 87.68 ( cm2/v•s ) , 3.1217 ( ohm•cm )
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
N-type ZnO films ( Ga v.s. Al )
◈ Growth condition
◈ Surface morphology
- OM
- AFM
◈ Crystallinity
- XRD rocking curve (FWHM)
◈ Electrical properties
- Hall measurement
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
◈ Growth conditions
▶ n-type Bulk layer growth
-Target :
① ZnO : Al (0.01 at %)
② ZnO : Ga (0.01 at %)
① ZnO : Al (0.01 at %)
② ZnO : Ga (0.01 at %)
( ~ 1um)
- Tg : 650 ℃
ZnO buffer layer (25nm)
- Pressure : 10 mTorr ( O2 + O3 mixture gas )
- Laser : 180 mJ / 4 Hz
Sapphire Substrate
- Ablation time : 2 hrs 20 min ( 1.22 Å / s )
▶ ZnO Buffer layer growth
- Target : undoped ZnO
- Pressure : 1m Torr ( O2 + O3 mixture gas )
- Tg : 850 ℃
- Laser : 180 mJ / 1 Hz
- Ablation time : 9 min ( 0.53 Å / s )
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
◈ AFM
Roughness rms : 14.174 nm )
① ZnO:Al
100 nm
② ZnO:Ga
( Roughness rms : 4.546 nm )
50 nm
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
◈ Roughness rms ( 10 ㎛ X 10 ㎛ )
Roughness rms (nm)
ZnO:Al
14.174
ZnO:Ga
4.546
◈ FWHM of XRD rocking curve
Omega rocking curve - FWHM (arcsec)
ZnO:Al
700 (0.1945°)
ZnO:Ga
513 (0.1425°)
◈ Hall
Concentration
(/cm3)
Mobility
(cm2/v•s)
Resistivity
(ohm•cm)
ZnO:Al
1.4050E+19
27.363
0.016231
ZnO:Ga
6.8788E+18
20.927
0.043497
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
1. SEM images ( ZLP-19, Tg = 700℃, 50mTorr ) + Tube furnace annealing (700 ℃, 1hr)
( ZnO:P / ZnO:Ga / ZnO thin buffer / Sapphire c-plane)
Evidence for particle growth upon annealing of Ga-doped ZnO?
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
pn junction formation and properties
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
IV for ZnMgO:P/ZnO junctions
-8
2.0x10
-8
o
3.0x10
500nm N-type ZnMgO:P(700 C)/200nm undoped ZnO(buffer)
Before annealing
2.0x10
-8
1.0x10
-8
Current (A)
Current (A)
o
500nm N-type ZnMgO:P(800 C)/200nm undoped ZnO(buffer)
-8 Before annealing
0.0
sample (b)
sample (c)
sample (d)
sample (e)
sample (f)
sample (g)
sample (h)
sample (i)
sample (j)
-8
-1.0x10
-8
-2.0x10
-6
-4
-2
0
2
-8
-2.0x10
-8
-3.0x10
-6
6
o
500nm N-type ZnMgO:P(900 C)/200nm undoped ZnO(buffer)
Current (A)
-9
4.0x10
-9
3.0x10
-9
sample (a)
sample (b)
sample (c)
sample (d)
sample (e)
sample (f)
sample (g)
sample (h)
Current (A)
-9
2.0x10
-9
1.0x10
0.0
-9
-1.0x10
-6
-4
-2
0
Bias (V)
-4
-2
0
2
4
-10
-9
5.0x10
sample (a)
sample (b)
sample (c)
sample (d)
sample (e)
sample (g)
sample (h)
-8
-1.0x10
Rectifying junctions with 3-4 V turn-on
-9
6.0x10
0.0
Bias (V)
Bias (V)
7.0x10
4
1.0x10
2
4
6
2.0x10
-10
1.5x10
-10
1.0x10
-11
5.0x10
0.0
o
500nm N-type ZnMgO:P(900 C)/200nm undoped ZnO(buffer)
before annealing
sample (a)
sample (b)
sample (c)
sample (d)
sample (e)
sample (g)
sample (h)
-11
-5.0x10
-10
-1.0x10
-10
-1.5x10
-10
-2.0x10
-10
-2.5x10
-6
-4
-2
0
Bias (V)
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
2
4
6
6
After annealing
Conductivity of N-type 500nm ZnMgO:P/200nm undoped ZnO buffer layer/sapphire
600oC
Annealing
temperature
700oC
700oC
ZnMgO:P
Increase
Decrease
Decrease
(current: 8*10-10 to 3*10-9 at 5V)
(current: 1*10-8 to 3*10-9 at 5V)
(current: 1.5*10-8 to 4*10-9 at 5V)
800oC
ZnMgO:P
Increase
Increase
Increase
(current: 4*10-9to 1.7*10-7 at 5V)
(current: 6*10-12 to 7*10-8 at 5V)
(current: 4*10-12 to 6*10-8 at 5V)
Increase
Increase
Increase
900oC
ZnMgO:P
(current:
5*10-12to
3*10-8
at 5V)
(current:
-7
3.5*10-12to
2.5*10-10
(current: 6*10-12to 2.8*10-10 at 5V)
at 5V)
-8
2.0x10
5.00x10
o
500nm N-type ZnMgO:P(800 C)/200nm undoped ZnO(buffer)
-7
1.5x10
-7
1.0x10
o
500nm N-type ZnMgO:P(900 C)/200nm undoped ZnO(buffer)
Annealed at 600C
Annealed at 700C
Annealed at 800C
Annealed at 600C
Annealed at 700C
Annealed at 800C
Current (A)
Current (A)
800oC
-8
5.0x10
0.0
-8
2.50x10
0.00
-8
-5.0x10
-7
-1.0x10
-6
-4
-2
0
2
4
6
Bias (V)
-10
3.0x10
-6
-4
-2
0
2
4
6
Bias (V)
o
500nm N-type ZnMgO:P(900 C)/200nm undoped ZnO(buffer)
-10
2.5x10
Annealed at 700C
Annealed at 800C
Rectifying turn-on at 3-4 volts
-10
Current (A)
-8
-2.50x10
2.0x10
-10
1.5x10
-10
1.0x10
-11
5.0x10
0.0
-11
-5.0x10
-6
-4
-2
0
2
4
6
ZnO LEDs for Solid State
Bias (V)Lighting Budget Period Review Sept 14, 2006
Annealing ZnMgO:P/ZnO/Al2O3 junctions
After annealing
600oC
conductivity
700oC
800oC
30 nm ZnO
increase
increase(current: 10-8 to 10-7 at -5V)
increase
100 nm ZnO
decrease
increase(current: 1.5*10-8 to 4*10-8 at -5V)
decrease
200 nm ZnO
decrease
decrease
decrease(current: 10-8 to 10-9 at -5V)
400 nm ZnO
decrease
decrease
decrease(current: 10-5 to 10-9 at -5V)
600C ZnMgO:P
decrease
decrease
decrease(current: 10-6 to 10-9 at -5V)
-8 500nm N-type ZnMgO:P(600oC)/200nm undoped ZnO(buffer)
8.0x10
-8
6.0x10
-8
4.0x10
-8
2.0x10
0.0
sample (a) annealing at 600C
sample (b) annealing at 700C
sample (c) annealing at 800C
Current (A)
Current (A)
-8 500nm N-type ZnMgO:P(500oC)/400nm undoped ZnO(buffer)
-8
-2.0x10
-8
-4.0x10
-8
-6.0x10
-8
-8.0x10
-6
-4
-2
0
2
4
6
4.0x10
-8
3.0x10
-8
2.0x10
-8
1.0x10
0.0
sample (a) annealing at 600C
sample (b) annealing at 700C
sample (c) annealing at 800C
-8
-1.0x10
-8
-2.0x10
-8
-3.0x10
-8
-4.0x10
-6
Bias (V)
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
-4
-2
0
Bias (V)
2
4
6
Research task: Investigate alternative p-type oxides as hole
injection materials
CuCrO2: possible alternative p-type oxide for hole injection
• Epitaxial film growth achieved
• Mg doping reported to produce p-type conductivity
10
CuCrO2 (104) peaks
Intensity (arb. units)
100000
Al2O3
(006)
CuCrO2
(006)
10000
CuCrO2
(003)
1000
CuCr2O4
(202)
CuCrO2
(009)
CuCr2O4
(303)
CuCrO2
(0012)
CuCr2O4
(101)
100
15
20
25
30
35
40
45
10
50
55
60
65
70
75
Intensity (arb. units)
XRD Omega-2Theta
8
6
4
2
1
Al2O3 (104) peaks
2Theta
0
0
30 60 90 120 150 180 210 240 270 300 330 360 390 420
Phi (Degree)
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
Research task: Investigate alternative p-type oxides as hole
injection materials
Ga-doped SnO2
Hall measurements:
P-type
Hole concentration 2x1019cm-3
(possible IP)
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
Changes to baseline plan in
Budget Period 2
• Experimental emphasis on epitaxial films
on sapphire
• Explored alternative p-type oxides as hole
injectors
• Explored light emission from implanted
ZnO and nanowires
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
Relationship of Budget Period 2 Tasks to Project Success
Task description
Specific activities
Relationship to overall project mission
Growth of p-type (Zn,Mg)O
films
Growth of phosphorus, arsenic, copper
doped (Zn,Mg)O films
Photoluminescence studies of P-, Asdoped ZnMgO films
Hall measurements of films
Annealing studies
Thin films needed for light-emitting pn
junction devices
Formation of pn homojunction
thin film structure
Grew (Zn,Mg)O pn junction structures
on sapphire
Grew (Zn,Mg)O pn junction structures
on single crystal ZnO substrates
Proof of concept device structure for
eventual heterostructure devices
Fabrication of pn homojunction
device
Identified materials and processes for
ohmic contacts
Identify processes for dry etching
Necessary for LED synthesis
Characterization of pn
homojunction
Measured IV characteristics
Investigate light emission from
junctions
Growth of p-(Zn,Mg)O/ZnO/n(Zn,Mg)O pn heterostructure
Grew multiple structures
Target device structure of program
Fabrication of p-(Zn,Mg)O/ZnO/n(Zn,Mg)O pn heterojunction
devices
Identified materials and processes for
ohmic contacts
Identify processes for dry etching
Target device structure of program
Understanding of pn junction properties
and performance
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
Status of project milestones in Budget Period 2
Title
Metric/Method of Verification
Milestone Status
Growth of p-type (Zn,Mg)O films
Achieve 10E17 cm-3 p-type carrier density
in ZnO film
Completed
Formation of pn homojunction thin film
structure
Optimize crystalline/polycrystalline pn
junction structure film growth process
with respect to IV
Demonstrated non-linear IV for
epitaxial and diffused samples.
Need better understanding of pn
junction formation
Fabrication of pn homojunction device
Achieve UV light emission from pn
homojunction device
Electroluminescence achieved for Nimplanted ZnO crystals and ZnO
nanowires the p-type polymer.
Additional work need for
epitaxial light emitting junctions.
Focus is on P:ZnO/Ga:ZnO
junctions
Characterization of pn homojunction
Determine efficacy of pn homojunction for
LED
Additional work needed to achieve
band-edge EL due to minority
carrier injection
Growth of p-(Zn,Mg)O/ZnO/n-(Zn,Mg)O
pn heterostructure
Optimization of epitaxial heterostructure
thin film junction
Highly crystalline buffer layer
developed.
Fabrication of p-(Zn,Mg)O/ZnO/n(Zn,Mg)O pn heterojunction
devices
Achieve nonlinear rectifying IV in pn
heterojunction device
Processing of mesa structures
demonstrated. Metal contact
technology developed
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
Status of project milestones in Budget Period 3
Task Title
Metric/Method of Verification
Status
Growth of p-type (Zn,Mg)O films
Achieve 10E18 cm-3 p-type carrier
density in ZnO film
Ongoing
Continue to explore P, As, N as
acceptor dopants
Formation of pn homojunction thin film
structure
Optimize polycrystalline pn junction
structure film growth process with
respect to IV
Lower priority
Proof of concept needed on epitaxial
structures
Fabrication of pn homojunction device
Achieve UV light emission from pn
homojunction device
Ongoing
Focusing on structures on single
crystal ZnO substrates
Characterization of pn homojunction
Determine efficacy of pn homojunction
for LED
Ongoing
Growth of p-(Zn,Mg)O/ZnO/n-(Zn,Mg)O
pn heterostructure
Optimization of epitaxial heterostructure
thin film junction
Ongoing
Optimization of polycrystalline
heterostructure thin film junction
Lower priority
Achieve nonlinear rectifying in pn
heterojunction device
Device fabrication protocol
estabilshed
Achieve UV light emission from pn
heterojunction
Ongoing
Fabrication of p-(Zn,Mg)O/ZnO/n(Zn,Mg)O pn heterojunction devices
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
Status of project milestones in Budget Period 3
(continued)
Task Title
Characterization of p-(Zn,Mg)O/ZnO/n(Zn,Mg)O pn heterojunction devices
Growth of p-CuGaO2/n-ZnO pn
heterostructure
Fabrication of CuGaO2/ZnO heterojunction
devices
Characterization of p-CuGaO2/n-ZnO
devices
Metric/Method of Verification
Status
Identify limiting factors for IV
nonlinearity and band-edge emission in
biased pn heterojunction
Ongoing
Determine the efficacy of pn
heterojunction for LED-based lighting
Ongoing
Achieve 10E18 cm-3 p-type carrier
density in epitaxial CuGaO2 film
Experiments shifted to CuCrO2 and
SnO2 epitaxial films as possible ptype hole injectors
Optimize epitaxial p-CuGaO2/n-ZnO
junction structure
To be initiated in Budget Period 3
with CuCrO2 and SnO2
Achieve nonlinear rectifying in pn
CuGaO2/n-ZnO heterojunction device
To be initiated in Budget Period 3
with CuCrO2 and SnO2
Achieve UV light emission from a
CuGaO2/ZnO pn heterojunction
To be initiated in Budget Period 3
with CuCrO2 and SnO2
Determine the efficacy of p-CuGaO2/nZnO LED devices for solid state lighting
To be initiated in Budget Period 3
with CuCrO2 and SnO2
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
Justification for continuation of project
• Progress made towards all milestones for Budget Period 2
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Achieved p-type ZnO with p = mid-1017/cm3
Light emission observed from implanted junctions
Homo- and heterojunction device fabrication process established
Epitaxy of alternative p-type hole injection material identified
• Original justification for project (promise of ZnO for light
emitting diodes) remains valid
– Reports in Applied Physics Letters of light emission in As-doped
ZnBeO LED
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
EL seen with current > 10 mA
Onset of nonlinear IV at 10 V,
not 3.2 V
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
ZnO LED Results for Other Groups
p-n LED Using Sputtering
[Jae-Hong Lim et al.]
Well-defined IV onset at ~ 3.2 V
Advance Material, 2006.
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
Overview of remaining Budget Periods
Year 1
Year 2
Year 3
Growth of p-type (Zn,Mg)O films (Norton)
Formation of pn homojunction (Norton)
Fabrication of pn homojunction device (Pearton)
Characterization of pn homojunction (Ren)
Growth of p-(Zn,Mg)O/ZnO/n-(Zn,Mg)O pn heterostructure (Norton)
Fab of p-(Zn,Mg)O/ZnO/n-(Zn,Mg)O pn heterojunction devices (Pearton)
Characterization of p-(Zn,Mg)O/ZnO/n-(Zn,Mg)O pn heterojunction devices (Ren)
Growth of p-CuGaO2/n-ZnO pn heterostructure (Ren)
Fab. of CuGaO2/ZnO heterojunction devices (Pearton)
Characterization of p-CuGaO2/n-ZnO devices (Ren)
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
Year 1
Year 2
Year 3
Growth of p-type (Zn,Mg)O films (Norton)
10E16 cm-3 p-type carrier density
10E18 cm-3 p-type carrier density
10E17 cm-3 p-type carrier density
Formation of pn homojunction (Norton)
Optimize epi junction structure
Optimize poly junction structure
Fabrication of pn homojunction device (Pearton)
Rectifying pn homojunction
Light emitting pn homojunction
Characterization of pn homojunction (Reen)
ID Limiting factors for band-edge emission
Determine efficacy of pn homojunction for LED
Growth of p-(Zn,Mg)O/ZnO/n-(Zn,Mg)O pn heterostructure (Norton)
Optimize epi junction structure
Optimize poly junction structure
Fab of p-(Zn,Mg)O/ZnO/n-(Zn,Mg)O pn heterojunction devices (Pearton)
Rectifying epitaxial pn heterojunction
Light emitting pn heterojunction
Characterization of p-(Zn,Mg)O/ZnO/n-(Zn,Mg)O pn heterojunction devices (Ren)
ID limiting factors for band-edge emission
Efficacy of pn heterojunction for LED
Growth of p-CuGaO2/n-ZnO pn heterostructure (Norton)
10E18 cm-3 p-type carrier density
Optimize epi junction structure
Fab. of CuGaO2/ZnO heterojunction devices (Pearton)
Rectifying pn junction
Light emitting pn heterojunction
Characterization of p-CuGaO2/n-ZnO devices (Ren)
Efficacy of p-CuGaO2/n-ZnO LED
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
•
DELIVERABLES
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The recipient will provide periodic, topical and final reports in
accordance with the “Federal Assistance reporting Checklist”
provided with the program solicitation.
The recipient will provide monthly e-mail correspondence with
the program manager that will indicate task and subtask updates,
expanded summary of project results, key milestones and
significant accomplishments, presentations and publications, site
visit and travel descriptions. The recipient will also provide
briefings for presentation upon request.
The recipient will present a technical paper at the DOE/NETL
Annual Contractor’s Review Meeting.
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006
Final product/commercialization
• Objective of project is to realized viable
LED technology based on ZnO pn
heterojunction
• Commercialization would be through a yet
to be determined industrial partner
ZnO LEDs for Solid State Lighting Budget Period Review Sept 14, 2006