Uncooled Infrared Photon Detection Concepts and Devices Viraj Jayaweera Piyankarage Department of Physics & Astronomy Georgia State University

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)


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


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


p+-GaAs emitter

Al0.57Ga0.43As barrierp++-GaAs contact

8-14 μmResponse

3-5 μmResponse

TC

MC

BC


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)


(A/cm2)


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


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)



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)


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 (%

)


0.00

0.02

0.04

Qua

ntu

m E

ffici

enc

y (%

)


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


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)


(A/cm2)


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


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)



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


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


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

Documents

Uncooled Infrared Photon Detection Concepts and Devices Viraj Jayaweera Piyankarage Department of Physics & Astronomy Georgia State University