Transcript Lecture Notes 17 - Array Detectors

Array Detectors
S W McKnight and C A DiMarzio
Focal Plane Arrays
Imaging Systems
H R Runciman, Thermal Imaging, CRC Press
Scanning vs. Staring Arrays
• Scanning Systems
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Point detector or linear array with scanning optics
Less complicated detector
Calibration easier
Scanning system expensive, fragile
Fast detector
• Staring Arrays
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Multiple detectors elements to capture pixels of image
Less complicated optics (lighter, smaller, no moving parts)
Longer integration time to increase sensitivity
Need multiplexer for signal read-out
• Charge-Coupled Devices (CCD’s)
– Charge transfer and collection
– Easier processing, less interconnects
• CMOS
– Individually addressed and processed pixels
– Less power
– No loss in tranfer
N-Channel FET Structure
S, Source
G, Gate
n+
D, Drain
n+
SiO2 Insulator
20-100mm
Channel: 2 to 500 mm
into page
P-Type Material
NMOS
Metal-Oxide-Semiconductor
B, Body
Channel Length
1 to 10 mm
Energy Band Picture of MOSFET
(No Bias—Flatband)
E
Ec
Ef
Ev
Metal
(Al or
Poly-Si)
Oxide
(SiO2)
Semiconductor
(p-Si)
z
Energy Band Picture of MOSFET
(Positive Gate Bias)
E
Фb2
Ec
Ef
Va
Фb1
Metal
(Al or
Poly-Si)
Oxide
(SiO2)
Ev
Semiconductor
(p-Si)
z
MOSFET Carrier Reconfiguration
(Depletion Bias)
E
Фb2
Va
Ec
Ef
Фb1
Depletion
Region
Oxide
Metal
(SiO2)
(Al or
Poly-Si)
Ev
Semiconductor
(p-Si)
z
Creation of Depletion Layer and
Inversion Channel
• Depletion layer forms within 1μs after bias
is applied
• Inversion channel created by thermally
generated carriers in ~ 1 s
• For times short compared to 1 s, nonequilibrium situation with depletion region
and empty channel.
• Carriers created by optical absorption or
external injection can be stored in well for
many ms.
Carrier Injection
Optical
Injection
E
Ec
Current
Injection
Vo-Vi
Ef
Va>Vt
Depletion
Region
Ev
Ef
Oxide
Metal
(SiO2)
(Al or
Poly-Si)
Semiconductor
(p-Si)
z
Charge-Coupled Device (CCD)
S
G
B
Channel Length
1 to 10 mm
D
S
D
B
~10 mm X nRows
Charge Transfer in CCD
J Allison, Electronic Engineering Semiconductors and Devices, McGraw-Hill
Streetman & Banerjee, Solid State Electronic Devices, Prentice-Hall
Focal Plane Arrays
• Monolithic Technology
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Detector and read-out CCD on same chip
Parallel processing (lower cost)
Improved ruggedness
Lower performance
Lower yield
• Hybrid Technology
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Detector and read-out fabricated separately and bonded
Single-device processing (more expensive)
Thermal mismatch
Choice of material for better performance
• HgCdTe for IR detector
• Silicon for CCD
Hybrid Technology
H R Runciman, Thermal Imaging, CRC Press
Hybrid Focal Plane Array
J L Miller, Principles of Infrared Technology, Van Norstrand Reinhold
Array Interconnects
J L Miller, Principles of Infrared Technology, Van Norstrand Reinhold
Platinum-Silicide Schottky Detectors
EB~0.22 eV ↔ λ=5.6 μ
PtSi
Si
hν
Streetman & Banerjee, Solid State Electronic Devices, Prentice-Hall
PtSi Array Detectors
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Low quantum efficiency (~1%)
Mid-Wave IR detection (1-5μ)
Long integration time (~1/60 s)
Good sensitivity ~0.05o C
Compatible with Si technology
Infrared Night Imaging
Sierra Pacific Infrared, Inc.
Infrared Night Imaging (2:15 AM)
Sierra Pacific Infrared, Inc.
Infrared Imaging—Circuit Hot Spot
Sierra Pacific Infrared, Inc.
Infrared Imaging—Water Damage
in Ceiling
Sierra Pacific Infrared, Inc.
Infrared Imaging—Tank Fluid Level
Sierra Pacific Infrared, Inc.
Infrared Imaging--- Building Energy
Efficiency
Sierra Pacific Infrared, Inc.
Infrared Imaging—Building Energy
Efficiency
Sierra Pacific Infrared, Inc.
Infrared Imaging—Biology
Sierra Pacific Infrared, Inc.
Infrared Imaging—Power Line
Faults
Sierra Pacific Infrared, Inc.
Infrared Medical Imaging—Patient
Recovering from Spinal Surgery
Sierra Pacific Infrared, Inc.