Imaging Beyond the Visible in the Short Wave Infrared with Indium Gallium Arsenide
Transcript of Imaging Beyond the Visible in the Short Wave Infrared with Indium Gallium Arsenide
Imaging Beyond the Visible in the Short Wave Infrared withIndium Gallium Arsenide
Martin H. Ettenberg, Ph. D., Director of Imaging Products
3490 US Rt. 1, Bldg. 12Princeton, NJ 08540Ph: 609-520-0610Fax: [email protected]
Imaging Beyond VisibleTM
www.sensorsinc.com
Topics
•What is the Short Wave Infrared?•How the Devices Are
Manufactured•Applications the Technology
Serves•R&D Topics
Imaging Beyond VisibleTM
www.sensorsinc.com
What is the Short Wave Infrared?
Imaging Beyond VisibleTM
www.sensorsinc.com
One-Dimensional InGaAs FPA
ROIC InGaAs PDA
Current Standard Sizes Available:1024 elements on 25 m pitch512 and 256 elements on 25 m and 50 m pitch1.7 m and 2.2 m cutoff commercially available2.6 m has been demonstrated at room temperature
Imaging Beyond VisibleTM
www.sensorsinc.com
2D Array Formats1.7 m cutoff commercially available
• 128x128x60 m (First array >12 years old)• 320x240x40 m (Old Industry standard)• 320x256x25 m (Industry standard)• 640x512x25 m (Industry standard)• Custom Sizes available through foundry services–1024x1024x17 m photodiode array- demonstrated
640x51225 m
320x24040 m
320x25630 m
128x12860 m
320x256, 25 µm
Imaging Beyond VisibleTM
www.sensorsinc.com
SWIR MicroCamera
Imaging Beyond VisibleTM
www.sensorsinc.com
What is InGaAs?An alloy of InAs and GaAs
5.4 5.5 5.6 5.7 5.8 5.9 6.0 6.10.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
GaP
InP
InAs
GaAsCut
off W
avel
engt
h (µ
m)
Lattice Constant (Å)
In.53Ga.47As
0.9 m
-1.
7 m
Imaging Beyond VisibleTM
www.sensorsinc.com
Epitaxy - A Core Capability, Especially for R&D
SUI’s Emcore LDM 180 Epitaxial Reactor6 -2”, 3 -3”, and 1 4” Wafer Capability
Imaging Beyond VisibleTM
www.sensorsinc.com
4” Wafer with 320x240 Arrays
Sensors Unlimited is the first to 4” InP Wafer Processing for Optoelectronic Devices
Imaging Beyond VisibleTM
www.sensorsinc.com
Nitride
Indium Phosphide
InGaAs
AR
Etch N-Channel
Light Light Light Light
Diffused - P-Type
Indium Bumps
Alloyed N-contact
P-ContactsOverlay (Step)
Back AR Coat
MULTIPLEXER
Process Cross-SectionBack Illuminated Devices
iP
N
Imaging Beyond VisibleTM
www.sensorsinc.com
The Difficulty of Fabricating Staring Detectors
•High signal-to-noise requires low dark current from the photodiode array
•The multiplexer limits the amount of signal gathering by the full-well capacity
•The user is limited by the number of scans that can be taken by the readout noise of the multiplexer
Imaging Beyond VisibleTM
www.sensorsinc.com
Full-well capacity of the multiplexer demands low dark current
•Linear Arrays <130 million electrons•Area Arrays <10 million electrons•1 nA is ~ 6 billion electrons/sec
–Dark signal collected at video rates (16ms) would fill a FPA array ~10x
•Lattice Matched InGaAs has dark current around 50 fA
Imaging Beyond VisibleTM
www.sensorsinc.com
Quantum Efficiency of InxGa1-xAs
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8
0.0
0.2
0.4
0.6
0.8
1.0
Si InGaAs1.7 InGaAs2.2 InGaAs2.5
Qua
ntum
Effi
cien
cy
Wavelength (µm)
Imaging Beyond VisibleTM
www.sensorsinc.com
What is InGaAs?An alloy of InAs and GaAs
5.4 5.5 5.6 5.7 5.8 5.9 6.0 6.10.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
GaP
InP
InAs
GaAsCut
off W
avel
engt
h (µ
m)
Lattice Constant (Å)
In.53Ga.47As
0.9 m
-1.
7 m
Imaging Beyond VisibleTM
www.sensorsinc.com
Device cross section for a 2.5m p-i-n detector structure
Long Wavelength InGaAsp-i-n Structure
Imaging Beyond VisibleTM
www.sensorsinc.com
Current Voltage Characteristics of Various InGaAs Alloys
1.00E -091.00E -081.00E -071.00E -061.00E -051.00E -041.00E -031.00E -02
0 0.5 1 1.5
R everse B ias (V)
Cu
rre
nt
De
ns
ity
(A/c
m )
2.2 m icron
2.0 m icron
1.7 m icron
2
RoA3000 -cm2
RoA150 -cm2
RoA80000 -cm2
RoA measurements use the electrical area not the optical area.
Imaging Beyond VisibleTM
www.sensorsinc.com
Why Image in the SWIR?
Military• Surveillance/Passive
Imaging• Covert Illumination• Range Gated Imaging• Free Space
Communication• Hyperspectral Imaging–Camouflage detection–Friend/Foe ID
Commercial• Inspection/Sorting–Agricultural products–Plastic Sorting–Semiconductors
• Telecommunications• Thermal Measurements• Spectroscopy
MilitaryApplications
Imaging Beyond VisibleTM
www.sensorsinc.com
Radiance of Night Sky
0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.00.00E+000
2.00E-011
4.00E-011
6.00E-011
8.00E-011
1.00E-010
1.20E-010
1.40E-010
1.60E-010
1.80E-010
night glow only night glow + .25 moon night glow + .50 moon night glow + .89 moon
Rad
ianc
e (W
/cm
2/sr
/.01µ
m)
Wavelength (µm)
Wavelength (µm)
Rad
ianc
e (W
/cm
2 /sr/
.01µ
m)
Vatsia, Mirshri, L. “Atmospheric Optical Environment”, Research and Development Technical Report ECOM-7023, September (1972)
Imaging Beyond VisibleTM
www.sensorsinc.com
Night Vision Under a Moonless SkyRoom temperature commercial camera SU320MX
Imaging Beyond VisibleTM
www.sensorsinc.com
Imaging Active Laser Sources
Imaging Beyond VisibleTM
www.sensorsinc.com
Fog PenetrationGunston Cove
VISIBLE IMAGERY SWIR 320x240
Imaging Beyond VisibleTM
www.sensorsinc.com
Multi-Sensor Image Fusion• Sophisticated Sensor Fusion
algorithms enable the user to identify the nature of objects in a scene in a sense through “coarse” hyperspectral imaging.
• Multisensor fusion enables imagers that are inherently more resistant to countermeasures.
SWIR
Visible
Thermal
Courtesy Dean Scribner, NRL
Commercial Applications
Imaging Beyond VisibleTM
www.sensorsinc.com
Commercial Applications
Commercial applications break into two major catagories, imaging and spectroscopy.
Imaging- Observing a scene to fabricate and imageOnline Processing- Detecting moistureThermal analysis- Metal Smelting, Furnace monitoringInspection of Phenomenology-Agriculture, Pharmaceutical,
SemiconductorsSpectral- Looking at multiple wavelengths to conduct an analysis
Telecommunication- Wavelength Division MultiplexingSorting- Plastic, AgricultureGeneral Spectroscopy- Scientific Investigation
Imaging Beyond VisibleTM
www.sensorsinc.com
Telecommunications
• Monitor and control WDM lasers
• Alignment of components–AWGs–Diode Lasers
• General Inspection– Light loss from
waveguides
From “High Resolution Fiber Grating Optical Network Monitor,” Koeppen,Wagener, Strasser, and DeMarco, Proceedings of NFOEC, Orlando (1998)
Imaging Beyond VisibleTM
www.sensorsinc.com
Optical Performance MonitorsAre Needed All Over The Network
Laser, 2
Laser, n
R, 1
R, 2
R, n
Transmit terminal
Laser, 1
Laser, 2 AA OADM A DCM
Las
er,
i
R,
iD
CM
MUX
Receive terminalAdd/drop node
DEMUX
A A
Amplifier
A
OP
M
OP
M
OP
M
OP
M
OP
M
OP
M
Imaging Beyond VisibleTM
www.sensorsinc.com
Industrial Process Monitors
•Plastic Sorting•Agricultural Sorting•Fruit and Vegetable
imperfections•Seed sorting
Imaging Beyond VisibleTM
www.sensorsinc.com
Thermal Imaging
•Lattice matched InGaAs is useful for imaging thermal processes above 80ºC–Too cold for silicon–Glass is transparent
•Glass manufacturing•Smelting of metals•Furnace monitoring
Imaging Beyond VisibleTM
www.sensorsinc.com
Inspection Applications• Many features can be seen in
the SWIR that are not apparent in the visible– Si is transparent to light
>1.1 m•Allows defects in Si to
be detected before processing•In process defects can
be identified•Emission microscopy
used in failure analysis– Some plastics are
transparent to SWIR light and not visible light making measurement of fill levels difficult
Imaging Beyond VisibleTM
www.sensorsinc.com
Renoir’s Luncheon of the Boating Party; courtesy of the Phillips Collection, Washington, DC
Imaging Through Paint(Art Restoration)
R&D
Imaging Beyond VisibleTM
www.sensorsinc.com
What needs Development?
•Longer wavelength cameras operating at room temperature–Long wavelength materials because of the defects
have very high dark current•New read out integrated circuits
–Handle large amounts of dark current–Large gain for high sensitivity applications–Advanced features
•High speed readouts•Wide Bandwidth detectors (communication and imaging)
Imaging Beyond VisibleTM
www.sensorsinc.com
Who Do We Work With?
•Princeton University•University of Virginia•Penn State•Rutgers UniversitySBIR/STTR and NIST Programs allow for
collaboration on long term research
Imaging Beyond VisibleTM
www.sensorsinc.com
Conclusions
•InGaAs imaging technology has seen major advances in the last 10 years–Imaging arrays capable of imaging at night–Avalanche Photodiode Arrays (APDs)
•InGaAs has many more opportunities for research to improve the technology–Longer wavelength materials–Lowering the dark current in all InGaAs alloys–Improving the ROIC circuits
•Imaging technologies will become critical in commercial and military applications