Upload
lora-claire-carr
View
221
Download
0
Embed Size (px)
Citation preview
Uncooled Infrared Photon Detection Concepts and Devices
Viraj Jayaweera Piyankarage
Department of Physics & Astronomy
Georgia State University
2
Outline
• Introduction
• Infrared Detectors based on
1. Dye-Sensitization of Nanostructured Semiconductors• Dye-sensitized NIR detector design, experimental results, and conclusion • 1/f Noise on DS nano structures
2. Displacement Currents in Semiconductor Quantum Dots (QDs) Embedded Dielectric Media
• Size quantization effects• QD capacitor based detector design, experimental results, and conclusion
3. Split-off Band Transitions in GaAs/AlGaAs Heterojunctions• High operating temperature split-off response observed from HEIWIP design for
17μm threshold wavelength• Uncooled split-off band detector design Experimental results, and conclusion
4. Free Carrier Absorption in GaSb Homojunctions• GaSb HIWIP detector design, experimental results, and conclusion
• Future Work
3
http://www.nasa.gov/centers/langley/science
Visible Micro Wave Near-IRNear-IR Mid-IRMid-IR Far-IRFar-IR
0.8 – 5 m 5 - 30 m 30 - 300 m
Wavelength
Electromagnetic Spectrum
4
–1-3 μm Short Wavelength Infrared SWIR
–3-5 μm Medium Wavelength Infrared MWIR
–5-14 μm Long Wavelength Infrared LWIR
–14-30 μm Very Long Wavelength Infrared VLWIR
–30-100 μm Far Infrared FIR
–100-1000 μm Sub-millimeter SubMM
IR Wavelength Range Classification
5
Applications
Infrared Body Temperature
Thermometer
Remote controller and receiver
http://www.netcast.com.hk/Products.htm
Visible Light Infrared
6Infrared image of Orion
Human suspect climbing over a fence at 2:49 AM in total darkness
Night vision helmet
Applications
Transverse, coronal, and sagittal views across the 3D absorption image of the infant, acquired at 780 nm.
www.medphys.ucl.ac.uk/research/borl/
brain imaging Blood Flow
7
Thermal analysis of a fluid tank level detection Close up image of a Intel Celeron chip
Faulty connection at power station
Applications
Bad Insulation spots
www.x20.org
www.x20.org
ºF
8
PhotonPhoton ThermalThermal
IR DetectorsIR Detectors
Different Types of Infrared Detectors
BolometricBolometric ThermoelectricThermoelectric
Pyroelectric Pyroelectric
PhotovoltaicPhotovoltaicPhoto- conductive
Photo- conductive
PhotoemissivePhotoemissive
9
Dye-Sensitized Near-Infrared Detectors
(DSNID)
10
Dye-sensitized electron injection to a semiconductor
Light induced charge carrier generation in a semiconductor
VB
CB
VB
CB
Semiconductor Dye
Direct and Sensitized Photo-Injection
HOMO
LUMO
LUMO = Lowest Unoccupied Molecular Orbital
HOMO = Highest Occupied Molecular Orbital
11
Dye-Sensitized Near-Infrared Detectors(DSNID)
n-TiO2 nanoparticles
Dye
p-CuSCN
V
n-type Dye p-type
Solid State Device (No Liquid Electrolyte)
TiO2IR dye CuSCN
12
Dye
Platinum or Gold layer
p-CuSCN
n-TiO2
Transparent Conducting Tin Oxide (CTO)
Glass
Glass TiO2 nanoparticles
Structure of a dye-sensitized IR Detector
Appl. Phys. Lett., Vol. 85, No. 23, (2004)
CTO
13
Appl. Phys. Lett., Vol. 85, No. 23, (2004)
Energy Level Diagram: n/D/p - Heterojunction
CB
VBCB
VB
S0
S*
Vacuum Energy (eV)
-1
-2
-3
-4
-5
-6
-7
-8
n-TiO2Dye p-CuSCN
14
Anionic Dyes(readily anchor to the TiO2 surface)
Cationic Dyes(Not directly anchor to TiO2
surface)
Anionic compounds used for cationic
Dyes
IR 783C38H46ClN2NaO6S2
2-[2-[2-Chloro-3-[2-[1,3-dihydro-3,3-dimethyl-1-(4-sulfobutyl)-2H-
indol-2-ylidene]-ethylidene]-1-cyclohexen-1-yl]-ethenyl]-3,3-dimethyl-1-(4-sulfobutyl)-3H-indolium hydroxide, inner salt
sodium salt
IR 792C42H49ClN2O4S
2-[2-[3-[(1,3-Dihydro-3,3-dimethyl-1-propyl-2H-indol-2-
ylidene)ethylidene]-2-(phenylthio)-1-cyclohexen-1-yl]ethenyl]-3,3-
dimethyl-1-propylindolium perchlorate
Mercurochrome (MC)C20H8Br2HgNa2O6
2′,7′-Dibromo-5′-(hydroxymercurio)fluorescein disodium salt
IR 820C46H50ClN2NaO6S2
2-[2-[2-Chloro-3-[[1,3-dihydro-1,1-dimethyl-3-(4-sulfobutyl)-2H-
benzo[e]indol-2-ylidene]-ethylidene]-1-cyclohexen-1-yl]-
ethenyl]-1,1-dimethyl-3-(4-sulfobutyl)-1H-benzo[e]indolium hydroxide inner salt, sodium salt
IR 1040C40H38BCl3F4N2
1-Butyl-2-[2-[3-[(1-butyl-6-chlorobenz[cd]indol-2(1H)-
ylidene)ethylidene]-2-chloro-1-cyclohexen-1-yl]ethenyl]-6-
chlorobenz[cd]indolium tetrafluoroborate
Bromopyrogallol Red (BPR)
C19H10Br2O9S
5′,5′′-Dibromopyrogallolsulfonephthalein
The number indicates the peak absorption wavelength in nanometers
IR Absorbing Dyes
15Appl. Phys. Lett., Vol. 85, No. 23, (2004)
0
1
2
3
0.65 0.75 0.85 0.95 1.05Wavelength (μm)
Re
sp
on
siv
ity
(m
A/W
)
MC + IR792
BPR + IR820
IR820 + IR1040
BPR + IR1040
IR783
IR820
Spectral Responsivity
Peak Detectivity = (9.0 ± 0.3) ×1010 cm Hz½ W-1
Conversion Efficiency = 0.4 %
16
Advantages Disadvantages
1. Low Cost
2. Fully Solid State
3. Detection wavelength can be tailored using the appropriate dye
4. Panchromatic sensitization using several dyes
5. Readily applicable to large area detectors
1. Slow Response
2. Poor long term stability
3. Although wavelength can be tailored, getting a sufficiently high extinction coefficient may not be easy.
4. HOMO level should be lower than p-type VB and LUMO should be higher than n-type CB
Advantages and Disadvantages of DSNID
17
Colloidal Quantum Dot Detectors
18
CdSe/ZnS Colloidal Quantum Dots (QDs) Emission Spectra
Size Quantization Effects
~4 nm ~15 nm
http://www.nanopicoftheday.org/2003Pics/QDRainbow.htm
Colloidal QDs are synthesized from precursor compounds dissolved in solutions.
19
TEM images of different size quantum dots (CdSe/ZnS) with emission wavelength at: (A) 525; (B) 540; (C) 590; (D) 652; and (E) 691 nm. Average diameter: (A) 4.2 nm; (B) 4.6 nm; (C) 6.7 nm; (D) 10.6 nm; (E) 20.1 nm. Scale bar: 20 nm.
Size Quantization Effects(H. Q. Wang et al. Journal of Colloid and Interface Science, 316 (2007) 622-627)
20
Y. Wang et al. J. Chem. Phys. 87 (1987)
PbS Colloidal QDs Bandgap vs. Particle size
Bulk PbS direct band gap = 0.41 eV (λt = 3 μm)
4 nm PbS QD = 1.2 eV (λt = 1 μm)
Wavelength (nm)
A. Margaret et al. Adv. Mater. 15 (2003)
21
QD Embedded Capacitor (QDEC) TypeIR Photodetectors
Micro Ammeter
Appl. Phys. Lett., 91, 063114 2007
Quantum Dot Battery
Dielectric Optical Chopper
Incoming IR radiation
22
Appl. Phys. Lett., 91, 063114 2007
TransparentConducting layer
(Fluorine-doped tin oxide)
Schematics of the QDEC TypeInfrared Photodetector
Glass
GlassPbS QD + Dielectric medium
Bottom Electrical Contact
Top Electrical Contact
Glass can be replaced with IR transmitting substrate such as Si, ZnSe, Sapphire, CaF2, MgF2, KRS
Possible dielectric materials:
• Paraffin Wax
• Silicon Nitride
• Silicon Oxide
Possible dielectric materials:
• Paraffin Wax
• Silicon Nitride
• Silicon Oxide
23
600 800 10000
50
100
150
200R
espo
nsiv
ity (
V/W
)
Wavelength (nm)
8.7 V 20 V 30 V 40 V
300 K
Spectral Responsivity of the QDEC IR Detector
Appl. Phys. Lett., 91, 063114 2007
PbS ~2 nm
24
Summary
Advantages Disadvantages
1. Low cost. (Fabrication does not involve sophisticated epitaxial growth
techniques)
2. Can be fabricated on flexible substrates.
3. No direct wire contact to QDs.
4. Sense only the variation of light. Insensitive to the background.
5. Multi band capability using a combination of QDs.
6. Spectral range can be extended using different QD materials (PbSe, InSb, HgCdTe).
1. Optical chopper not practical for some applications.
2. Density of QDs can not increases arbitrarily. After a threshold value it start to conduct.
25
HEIWIP Free Carrier Detectors (Heterounction Interfacial Workfunction Internal Photoemission)
26
HEIWIP Detectors (Heterounction Interfacial Workfunction Internal Photoemission Detectors)
p+-GaAs AlxGa1-xAs
VB
Δ
VBEF
Zero Bias
p+-GaAs AlxGa1-xAs
Δ
Biased
Absorption is due to free carriersInterface is sharp (no space charge)
Barrier formed by Heterojunction (p-type)
Internal workfunction Δ comes from Al fraction (x) and doping
APL 78, 2241 (2001)
APL 82, 139 (2003)
Emitter Barrierh
hν
27
p+-GaAs AlxGa1-xAs
VBΔx
VBEF
Free Carrier Threshold of HEIWIP Detector
Al fraction x = 0.090λt = Threshold Wavelength
Δd
Wavelength (μm)
Emitter Barrier
NA = 3×1018 cm-3 Doped p+ GaAs Emitters
Re
spo
nsi
vity
(a
.u.)
λt
Δ = Δd + Δx
28
Split-off Band Detectors
29
SO Band
QWIP (GaAs/AlGaAs)
HH Band LH
Band
E
k
Intersubband levels
SO Band
QWIP (GaAs/AlGaAs)
HH Band LH
Band
E
k
Intersubband levels
Split-off Band
Conduction Band
Extrinsic(Si:P)
E
k
Light Hole Band
Impurity Band
Heavy Hole Band
Split-off Band
Conduction Band
Extrinsic(Si:P)
E
k
Light Hole Band
Impurity Band
Heavy Hole Band
Heavy Hole Band
Split-off Band
Conduction Band
INTRINSIC(InSb, HgCdTe)
E
k
Light Hole Band
Heavy Hole Band
Split-off Band
Conduction Band
INTRINSIC(InSb, HgCdTe)
E
k
Light Hole Band
Heavy Hole Band
Split-off Band
Conduction Band
INTRINSIC (InSb, HgCdTe)
E
k
Light Hole Band
Infrared Detector Mechanisms
Split-off Band
Conduction Band
Extrinsic (Si:P)
E
k
Light Hole Band
Impurity Band
Heavy Hole Band
SO Band
QWIP (GaAs/AlGaAs)
HH Band LH
Band
E
k
Intersubband levels
Split-off Band
Conduction Band
Split-Off
E
k
Light Hole Band
Heavy Hole Band
EF
30
Split-off Detector Threshold Mechanisms
SO Band
Ef
EBL/H
LH Band
CB
HH Band
EBSO
k
Indirect absorption followed by scattering and escape
Threshold Energy EESO - Ef
SPLIT-OFFIntra-valence Transitions
Direct absorption followed by scattering and escape
Threshold Energy EESOf - Ef
Indirect absorption followed by escape without scattering
Threshold Energy EBSO - Ef
EESO
E
p+-GaAs AlGaAs
SO
L /H
IR Photon excites holes from the light/heavy hole bands to the split-off band (Solid Arrow)Excited holes can scatter into the light/heavy hole bands (Dashed Arrow) and then escapeIR Photon excites holes from the light/heavy hole bands to the split-off band (Solid Arrow)Excited holes can scatter into the light/heavy hole bands (Dashed Arrow) and then escape, or escape directly from the split-off band
Appl. Phys. Lett., 89 131118 (2006)
31
Schematics of the Detector
SubstrateGaAs
Bottom Contact p++ GaAs
p+ GaAs (emitter)
AlGaAs (barrier)
Top Contact p++ GaAs
N Period
s
400 μm
400 μm
Au contact layers
<2.5μm
RBias
32
2 3 4 50.00
0.02
0.04
Abs
orpt
ion
Wavelength (m)
Absorption and Conversion Efficiency(Initial Sample 1332, λt = 17 μm)
Al Fraction
x
Δ (meV)
λt
(μm)
GaAsEmitter AlxGa1-xAs
Barrier Thickness
(Å)
No of Periods
NDoping (cm-3) Thickness (Å)
0.15 73 17 3×1018 188 1250 12
Split-off
Free Carrier α λ
2
4 8 12 160.00
0.01
0.02
Con
vers
ion
Effi
cie
ncy
Wavelength (m)
Free Carrier
Split-off
33
Sample#
Al Fraction
x
Δ (meV)
λt (μm)
GaAsEmitter AlxGa1-xAs
Barrier Thickness
(Å)
No of Periods
Doping (cm-3) Thickness (Å)
SP1 0.28 155 8 3×1018 188 600 30
Different Free Carrier Threshold (λt) Samples
SP1
155 meV
SO Band
L /H Band
SP2 0.37 207 6 3×1018 188 600 30
SP3 0.57 310 4 3×1018 188 600 30
SP2
207 meV
SP3
310 meV
365 meV
365 meV
365 meV
Appl. Phys. Lett., 93 021105 (2008)
34
Sample#
Δ λtOperating
Temperature
Dynamic Resistance @ 1V (Ω)
Dark Current Density @ 1V
(A/cm2)
Responsivity(mA / W)
D*(Jones)
(meV) (μm)
SP1 155 8 140 787 ± 1 0.663 ± 0.003 2.3 ± 0.1 (2.1 ± 0.1)×106
Results of Different λt Samples
Operating threshold dark current ~1 A/cm2
Design flexibility for higher D* or higher operating temperature
SP2 207 6 190 913 ± 1 0.875 ± 0.003 2.7 ± 0.1 (1.8 ± 0.1)×106
SP3 310 4300 1138 ± 1 0.563 ± 0.003 0.29 ± 0.1 (6.8 ± 0.1)×105
150 (1.7±0.1) ×109 (3.4±0.1)×10-7 (2.1±0.1)×10-3 (2.2 ±0.1)×1010
20 80 140 200 260 32010-9
10-7
10-5
10-3
10-1
101
SP1
Da
rkcu
rre
nt D
en
sity
at 1
V b
ias
(A c
m-2)
Temperature (K)
20 80 140 200 260 32010-9
10-7
10-5
10-3
10-1
101
SP1 SP2
Da
rkcu
rre
nt D
en
sity
at 1
V b
ias
(A c
m-2)
Temperature (K)
20 80 140 200 260 32010-9
10-7
10-5
10-3
10-1
101
SP1 SP2 SP3
Da
rkcu
rre
nt D
en
sity
at 1
V b
ias
(A c
m-2)
Temperature (K)
35
2 3 40.0
0.1
0.2
0.3 1 V 2 V 3 V 4 V
Res
pons
ivity
(m
A/W
)
Wavelength (m)
300 K
Room Temperature Response( SP3: 4 μm Free Carrier Threshold )
SP3
SO Band
Ef
L/H
LH Band
CB
HH Band
SPLIT-OFFIntra-valence Transitions
SO
k
ESO – Ef = 370 meV 3.4 μm
ESOf – Ef = 420 meV 2.9 μm
Appl. Phys. Lett., 93 021105 (2008)
36
Responsivity Comparison for Different λt Samples
Sample#
Free Carrier Threshold
(μm)
Al Fractionx
Δ (meV)
SP1 8 0.28 155
SP2 6 0.37 207
SP3 4 0.57 310
2 3 4 50
1
2
SP1 140 K SP2 190 K SP3 330 K
Res
pons
ivity
(m
A /
W)
Wavelength (m)2 3 4 5
0
1
2 SP1 140 K SP2 150 K
Res
pons
ivity
(m
A /
W)
Wavelength (m)
37
2 3 40.0
0.1
0.2
0.3R
espo
nsiv
ity (
mA
/W)
Wavelength (m)
SP3330 K
2 3 40.0
0.1
0.2
0.3R
espo
nsiv
ity (
mA
/W)
Wavelength (m)
SP3330 K
4 VNoise level3 V2 V1 V
Above Room Temperature Operation
38
Material ΔSO (meV) λSO (μm)
InAs 410 3.2
GaAs 340 3.6
AlAs 300 4.1InP 110 11GaP 80 16AlP 70 18GaN 20 62
AlN 19 65
InN 3 410
Possibility of a room temperature dual band detector for atmospheric windows 3-5 and 8-14 m using Arsenides & Phosphides
Different Material will Cover Different Split-off Ranges
In1-xGaxAsyP1-y110 - 379
(0.11+0.421y-0.152y²)3.3 - 11
In1-xGaxP93 - 101
0.101+0.042x-0.05x2 12.3 - 13.3
39
Summary
• High Operating Temperature (Uncooled or TE Cooled)
• Tunability (Wavelength, Detectivity, Operating Temperature)
• Well Developed Materials, Readout Circuits, and Integrated Circuits
• High Performance
40
GaSb Homojunction Far-IR (THz)
Detectors
41
p+-GaSb UndopedGaSb
VB
Δ
VBEF
Zero Bias
p+-GaSb UndopedGaSb
Δ
Biased
Emitter Barrier
Absorption is due to free carriers
Barrier formed by Homo-junction (p-type)
Δ comes from doping
HIWIP(Homojunction Interfacial Workfunction Internal Photoemission Detectors)
h
hν
A.G.U. Perera et al., JAP (77) 915 (1995)
42
0.05 μm
0.05 μm
5×1018cm-3 p++ GaSb Substrate
2×1018cm-3 p+ emitter
Undoped-GaSb barrier
2×1018cm-3 p+ emitter
5×1018cm-3 p++
2 μm
0.1 μm
Metalcontact
Grown by OMCVD
GaSb HIWIP Far-IR (THz) Detector
Δ
GaS
b
p+ G
aSb p+
GaS
b
Top
Cont
act
Botto
m
Cont
act
ΔE
VAppl. Phys. Lett. 90, 111109 (2007)
43
0
2
4
6
8
10
20 30 40Wavelength (m)
Res
pons
ivity
(A
/W)
3.7 V3.4 V3.0 V2.0 V1.0 V
T = 4.9 K
15 7Frequency (THz)
10
0
2
4
6
8
10
20 30 40Wavelength (m)
Res
pons
ivity
(A
/W)
3.7 V3.4 V3.0 V2.0 V1.0 V
T = 4.9 K
15 7Frequency (THz)
10
Appl. Phys. Lett. 90, 111109 (2007)
GaSb HIWIP Far-IR (THz) Response
Peak Detectivity at 36 μm = (5.7 ± 0.1)×1011 cm Hz½ W-1
Conversion Efficiency = 33 %
44
10
10
10
10
10
10
20 80 140 200Wavelength (m)
Res
pons
ivity
(A
/W)
1
0
-1
-2
-3
-4
T = 4.9 K
3.0 V2.0 V1.0 V97 μm
15 1.5Frequency (THz)
4 2
10
10
10
10
10
10
20 80 140 200Wavelength (m)
Res
pons
ivity
(A
/W)
1
0
-1
-2
-3
-4
T = 4.9 K
3.0 V2.0 V1.0 V97 μm
15 1.5Frequency (THz)
4 2
GaSb HIWIP Far-IR (THz) Response
45
101
102
103
104
10520 40 60 80 100
12 630
Frequency (THz)
Wavelength (m)
Ab
sorp
tion
co
effi
cie
nt
cm
-1
3
3.4x1018 cm-3
1.8x1018 cm-3
1.2x1018 cm-3
5.0x1017 cm-3
1.6x1017 cm-3
GaSb
101
102
103
104
10520 40 60 80 100
30 12 6 3
Frequency (THz)
Wavelength (m)
Abs
orpt
ion
coef
ficie
nt
(cm
-1)
3x1018 cm-3
5x1018 cm-3
8x1018 cm-3
GaAs
Why GaSb ?
GaSb THz Absorption
46
InGaSb/GaSb Heterojunctions
Emitter Barrier Offset
GaAs AlxGa1-xAs 530x meV
GaN AlxGa1-xN 800x meV
InxGa1-xSb GaSb 40x meV
InGaSb/GaSb has a small valance band offset
Much better for THz heterojunctions
Barrier is ~4 meV for 1 THz
Corresponds to 10% variation In fraction in Sb material
< 1% Al fraction for As, N materials 0
100
200
300
400
500
0.00 0.05 0.10 0.15 0.20
x
Th
resh
old
wa
vele
ng
th
47
Summary
• Higher absorption coefficient compared to GaAs
• High performance
Responsivity 9.7 A/W, Detectivity (5.7 ± 0.1)×1011 Jones at 36 μm and 4.9 K.
• Wavelength tailorability
• Design with 14 μm threshold expected to be work at TE cool temperatures.
• InGaSb/GaSb heterojunction has a small valance band offset much better for THz designs
48
Future Works
49
200 400 600 800 1000 1200 14000
4
8
12
16
ZnO
300 K
0.2 V 0.5 V 1 V
Res
po
nsi
vity
(kV
/ W
)
Wavelength (nm)
~ 3 nm PbS QD
ITOITO
Glass Substrate
~10 μm
ZnO
Colloidal Quantum Dot Based UV-NIRDual-Band Detector
Photo Conductive
PbS QDs
200 400 600 800 1000 1200 14000
1
2
3
4
5ZnO
0.5V 1V
Re
sp
on
siv
ity
(k
V/W
)
Wavelength(nm)
300 K
In preparation to Appl. Phys. Lett.
50
GaAs substrate
p++-In0.49Ga0.51P contact
Al0.8Ga0.2As barrier
p+-In0.49Ga0.51P emitter
p++-InGaP emitter
p++-GaAs contact
Al0.8Ga0.2As barrier
p+-GaAs emitter
Al0.57Ga0.43As barrierp++-GaAs contact
8-14 μmResponse
3-5 μmResponse
TC
MC
BC
Al0.57Ga0.43As barrier
Al 0.
8G
a0.
2A
s
Al 0.
8G
a0.
2A
s
p+-I
n0.
49G
a0.
51P
Al 0.
57G
a 0.4
3As
Al 0.
57G
a 0.4
3As
p++-GaAs
p+-GaAs
p++-GaAs
p++-I
n0.
49G
a0.
51P
Proposed dual band detector for 3-5 and 8-14 μm atmospheric windows using Arsenides & Phosphides
51
1. P. V. V. Jayaweera, S. G. Matsik, A. G. U. Perera, H. C. Liu, M. Buchanan and Z. R. Wasilewski "Uncooled infrared detectors for 3-5 μm and beyond", Applied Physics Letters 93, 021105, (2008)
2. P. V. V. Jayaweera, A.G.U. Perera and K. Tennakone "Why Gratzel′s cell works so well” Inorganica Chimica Acta, 361, 707-711, (2008)
3. A. G. U. Perera, P. V. V. Jayaweera, G. Ariyawansa, S. G. Matsik, M. Buchanan and H. C. Liu), "Room Temperature Nano and Micro Structure Photon Detectors", Microelectronics Journal, In Press, (2008)
4. P. V. V. Jayaweera, A. G. U. Perera, and K. Tennakone, "Displacement currents in semiconductor quantum dots embedded dielectric media: A method for room temperature photon detection" Applied Physics Letters 91, 063114-3, (2007)
5. P. V. V. Jayaweera, S. G. Matsik, and A. G. U. Perera, Y. Paltiel, Ariel Sher and Arie Raizman, H. Luo, and H. C. Liu, “GaSb homojunctions for Far-IR (THz) Detection” Applied Physics Letters, 90, 111109, (2007)
6. P. V. V. Jayaweera, P.K.D.D.P. Pitigala, M.K.I. Seneviratne, A. G. U. Perera and K. Tennakone “1/f Noise in dye-sensitized solar cells and NIR photon detectors” Infrared Physics & Technology, 50, 270-273 (2007)
7. P. V. V. Jayaweera, S.G. Matsik, K. Tennakone, A.G.U. Perera, H.C. Liu and S. Krishna ) "Spin split-off transition based IR detectors operating at high temperatures" Infrared Physics & Technology, 50, 279-283 (2007)
8. A. G. U. Perera, S. G. Matsik, P. V. V. Jayaweera, K. Tennakone, H. C. Liu, M. Buchanan G. Von Winckel, A. Stintz, and S. Krishna) “High Operating Temperature Split-off Band Infrared Detectors” Applied Physics Letters, 89, 131118, (2006)
9. P. V. V. Jayaweera, P. K. D. D. P. Pitigala, A. G. U. Perera and K. Tennakone "1/f noise and dye-sensitized solar cells", Semicond. Sci. Technol. 20, L40–L42, (2005)
10. P. V. V. Jayaweera, A. G. U. Perera, M. K. I. Senevirathna, P. K. D. D. P. Pitigala, and K. Tennakone, “Dye-sensitized near-infrared room-temperature photovoltaic photon detectors" Applied Physics Letters 85 (23), 5754-5756, (2004)
List of Publications Relevant to Presented Results
52
Acknowledgement
Advisor:
• Dr. Unil Perera
Committee
• Dr. Vadym M. Apalkov
• Dr. Douglas Gies
• Dr. Xiaochun He
• Dr. Kirthi Tennakone
• Dr. Brian D. Thoms
Department Chair:
• Dr. H. R. Miller
Associate Dean:
• Dr. William H. Nelson
Group Members
Dr. Steven Matsik, Dr. Gamini Ariyawansa, Ranga Jayasinghe, Dulipa Pitigala, Laura Byrum, Jiafeng Shao, Dr. Manmohan Singh, Greggory Rothmeier
Group Members
Dr. Steven Matsik, Dr. Gamini Ariyawansa, Ranga Jayasinghe, Dulipa Pitigala, Laura Byrum, Jiafeng Shao, Dr. Manmohan Singh, Greggory Rothmeier
Department Staff: Yvette Hilaire, Felicia Watts, Carola Butler, Duke Windsor
Instrument Shop:Charles Hopper, Peter Walker, Dwayne Alan Torres
Department Staff: Yvette Hilaire, Felicia Watts, Carola Butler, Duke Windsor
Instrument Shop:Charles Hopper, Peter Walker, Dwayne Alan Torres
53
The End
Oct. 28 2008
54
55
http://sales.hamamatsu.com/en/support/technical-notes.php
67
Sample#
Δ λt
Operating Temperature
Dynamic Resistance
@ 1V(Ω)
Dark Current Density @ 1V
(A/cm2)
Responsivity(mA / W)
D*(Jones)
(meV) (μm)
SP1 155 8 140 787 0.663 2.3 2.1×106
SP2 207 6 190 913 0.875 2.7 1.8×106
SP3 310 4300 1138 0.563 0.29 6.8×105
150 1.74×109 3.4×10-7 0.0021 2.2×1010
Results of Different λt Samples
20 80 140 200 260 32010-9
10-7
10-5
10-3
10-1
101
SP1 SP2 SP3
Da
rk C
urr
en
t De
nsi
ty
at 1
V b
ias
(A c
m-2)
Temperature (K)
Operating threshold dark current ~1 A/cm2
Design flexibility for higher D* or higher operating temperature
68
Wavelength (nm)
PbS Colloidal QDs AbsorptionA. Margaret et al. Adv. Mater. 15 (2003) 1844
Bulk PbS direct band gap = 0.41 eV
69
101
102
103
104
10520 40 60 80 100
12 630
Frequency (THz)
Wavelength (m)
Ab
sorp
tion
co
effi
cie
nt
cm
-1
3
3.4x1018 cm-3
1.8x1018 cm-3
1.2x1018 cm-3
5.0x1017 cm-3
1.6x1017 cm-3
GaSb
101
102
103
104
10520 40 60 80 100
30 12 6 3
Frequency (THz)
Wavelength (m)
Abs
orpt
ion
coef
ficie
nt
(cm
-1)
3x1018 cm-3
5x1018 cm-3
8x1018 cm-3
GaAs
Why GaSb ?
GaSb THz Absorption
70
InGaSb/GaSb Heterojunctions
Emitter Barrier Offset
GaAs AlxGa1-xAs 530x meV
GaN AlxGa1-xN 800x meV
InxGa1-xSb GaSb 40x meV
InGaSb/GaSb has a small valance band offset
Much better for THz heterojunctions
Barrier is ~4 meV for 1 THz
Corresponds to 10% variation In fraction in Sb material
< 1% Al fraction for As, N materials 0
100
200
300
400
500
0.00 0.05 0.10 0.15 0.20
x
Th
resh
old
wa
vele
ng
th
71
200 400 600 800 1000 1200 14000
2
4
6
8 ZnO
Res
po
ns
ivit
y (
kV /
W)
Wavelength(nm)
T=300 K
~3 nm PbS QD
Bias =2 V
Colloidal Quantum Dot based UV-NIRDual-band Detector
ITOITO
Glass Substrate
~10 μm
ZnO
Photo Conductive
PbS QDs
72
(H. Q. Wang et al. Journal of Colloid and Interface Science, 316 (2007) 622-627)
UV–visible absorption and fluorescence spectra of different CdSe QDs synthesized by changing the nucleation time (nucleation time from 10 to 360 s, emission from 514 to 680 nm), measured at room temperature.
Size Quantization Effects
73
Al Fraction
x
Δ (meV)
λt (μm)
GaAsEmitter AlxGa1-xAs
Barrier Thickness
(Å)
No of Periods
Doping (cm-3) Thickness (Å)
0.12 62 20 1×1018 188 1250 16
2 3 4 50.00
0.02
0.04
Qua
ntu
m E
ffici
enc
y (%
)
Wavelength (m)2 3 4 5
0.00
0.02
0.04
Qua
ntu
m E
ffici
enc
y (%
)
Wavelength (m)2 3 4 5
0.00
0.04
0.08
0.12
Ab
sorp
tion
Wavelength (m)
2 3 4 50.00
0.04
0.08
0.12
Ab
sorp
tion
Wavelength (m)
Split-off
Free Carrier α
λ2
Con
vers
ion
Effi
cien
cy
Absorption and Conversion Efficiency(Initial Sample HE0204, λt = 20 μm)
74
Split-off Response for the 20 μm Free Carrier Threshold Detector
SO Band
Ef
ΔL/H
LH Band
CB
HH Band
SPLIT-OFFIntra-valence Transitions
ΔSO
k
Appl. Phys. Lett., 89, 131118 (2006)
ESO – Ef = 370 meV 3.4 μm
ESOf – Ef = 420 meV 2.9 μm
ΔSO – Ef = 420 meV 2.9 μm
2 3 4 50.0
0.2
0.4
0.6 80 K 90 K 100 K 105 K 120 K 130 K
Res
pons
e (m
A/W
)
Wavelength (m)
HE0204
Re
spo
nsi
vity
(m
A /
W)
E
75
Outline
• Introduction
• Infrared Detectors based on
1. Dye-Sensitization of Nanostructured Semiconductors• Dye-sensitized NIR detector design, experimental results and summery • 1/f Noise on DS nano structures
2. Displacement Currents in Semiconductor Quantum Dots (QDs) Embedded Dielectric Media
• Size quantization effects• QD capacitor based detector design, experimental results and summery
3. Split-off Band Transitions in GaAs/AlGaAs Heterojunction• High operating temperature split-off response observed from HEIWIP design for 17
μm threshold wavelength• Uncooled split-off band detector design Experimental results and Summery
4. Free Carrier Absorption in GaSb Homojunction• GaSb HIWIP detector design, experimental results and summery
• Future Works
76
Advantages over other 3-5 µm Detectors
Arsenides will be used for 3 – 5 μm rangematerial, readout circuits, and Integrated electronics already developed
Detector Advantage Proposed Split-off Detector
InSb
D* =1x1011 Jones
77 K Operating Temperature
300 K
HgCdTe
D* =3x1010 Jones
77-240 K
~4% Bad Pixels (256x256)
Operating Temperature
Uniformity
300 K
~0.1% Bad Pixels (600x512)
PbSe
D* =3x1010 Jones
Threshold depends on Temperature
Better Stability Threshold fixed by split-off energy
77
-16
-14
-12
-10
0.02 0.04 0.06
1/T (K-1)
ln (I
/T1.
5 )
0
2
4
6
8
10
0 1 2 3 4Bias (V)
Peak
Res
pons
ivity
(A/W
)
78
Sample#
Δ(meV)
λt
(μm)Tmax
(K)Δ/kTmax
Dynamic Resistance @
1V(Ω)
Dark Current Density @ 1V
(A/cm2)
Responsivity(mA / W)
D*(Jones)
SP1 155 8 140 12.8 787 ± 1 0.663 ± 0.003 2.3 ± 0.1 (2.1 ± 0.1)×106
SP2 207 6 190 12.6 913 ± 1 0.875 ± 0.003 2.7 ± 0.1 (1.8 ± 0.1)×106
SP3 310 4 300 12.0 1138 ± 1 0.563 ± 0.003 0.29 ± 0.01 (6.8 ± 0.1)×105
Results of Different λt Samples
20 80 140 200 260 32010-9
10-7
10-5
10-3
10-1
101
SP1 SP2 SP3
Da
rk C
urr
en
t De
nsi
ty
at 1
V b
ias
(A c
m-2)
Temperature (K)
Operating threshold dark current ~1 A/cm2
Design flexibility for higher D* or higher operating temperature
0
100
200
300
400
500
600
0 5 10 15 20 25 30
Threshold Wavelength (um)
Ma
xim
um
Op
era
tin
g
Te
mp
era
ture
(K
)
Appl. Phys. Lett., 93 021105 (2008)
79
Internal Photoemission Detectors
Type I - Nd < Nc ( ECn+ > EF )
Nd : Doping of Emitter
Nc : Mott’s Metal Insulator Transition
EC : Band gap narrowing
= (ECn+ - EF) + EC
Ec
n+
EcEc
i
h
e
EF
Unbiased
Biased
A.G.U. Perera et al., JAP (77) 915 (1995)
80
Type II - Nc < Nd < N0 ( ECn+ < EF < EC
i )
Nd : Doping density in the Emitter/Absorber
Nc : Mott’s Metal Insulator Transition
N0 : Critical concentration
= Eci - EF
Fermi level is above the conduction band edge of the emitter
Emitter becomes semi-metallic
Infrared absorption is due to free carriers
A.G.U. Perera et al., JAP (77) 915 (1995)
81
Fermi level is above the conduction band edge of the barrier
Conduction band edge of the Emitter and the barrier become degenerate
Space charge region at the n++ - i interface forms the barrier
Barrier height depends on the concentration and the applied field
Type III - Nd > N0 ( EF > ECi )
Nd : Doping concentration of
the Emitter/ Absorber
N0 : Critical concentration
S. Tohyama et al., IEDM Tech. Dig. p.82 (1988)
82
GaSb GaSb
VB
EF
GaSbCB
p+-GaSb
VBEF
CB