John K. Liu

640/spl times/486 long-wavelength two-color GaAs/AlGaAs quantum well infrared photodetector (QWIP) focal plane array camera

We have designed and fabricated an optimized long-wavelength/very-long wavelength two-color quantum well infrared photodetector (QWIP) device structure. The device structure was grown on a 3-in semi-insulating GaAs substrate by molecular beam epitaxy (MBE). The wafer was processed into several 640/spl times/486 format monolithically integrated 8-9 and 14-15 /spl mu/m two-color (or dual wavelength) QWIP focal plane arrays (FPAs). These FPAs were then hybridized to 640/spl times/486 silicon CMOS readout multiplexers. A thinned (i.e., substrate removed) FPA hybrid was integrated into a liquid helium cooled dewar for electrical and optical characterization and to demonstrate simultaneous two-color imagery. The 8-9 /spl mu/m detectors in the FPA have shown background limited performance (BLIP) at 70 K operating temperature for 300 K background with f/2 cold stop. The 14-15 /spl mu/m detectors of the FPA reaches BLIP at 40 K operating temperature under the same background conditions. In this paper we discuss the performance of this long-wavelength dualband QWIP FPA in terms of quantum efficiency, detectivity, noise equivalent temperature difference (NE/spl Delta/T), uniformity, and operability.

640

Epitaxially grown self-assembled InAs-InGaAs-GaAs quantum dots (QDs) are exploited for the development of large-format long-wavelength infrared focal plane arrays (FPAs). The dot-in-a-well (DWELL) structures were experimentally shown to absorb both 45deg and normal incident light, therefore, a reflection grating structure was used to enhance the quantum efficiency. The devices exhibit peak responsivity out to 8.1 mum, with peak detectivity reaching ~1times1010 Jones at 77 K. The devices were fabricated into the first long-wavelength 640times512 pixel QD infrared photodetector imaging FPA, which has produced excellent infrared imagery with noise equivalent temperature difference of 40 mK at 60-K operating temperature

\,\times\,

Mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) 1024 × 1024 pixel quantum well infrared photodetector (QWIP) focal planes have been demonstrated with excellent imaging performance. The MWIR QWIP detector array has demonstrated a noise equivalent differential temperature (NEΔT) of 17 mK at a 95 K operating temperature with f/2.5 optics at 300 K background and the LWIR detector array has demonstrated a NEΔT of 13 mK at a 70 K operating temperature with the same optical and background conditions as the MWIR detector array after the subtraction of system noise. Both MWIR and LWIR focal planes have shown background limited performance (BLIP) at 90 K and 70 K operating temperatures respectively, with similar optical and background conditions. In this paper, we will discuss the performance in terms of quantum efficiency, NEΔT, uniformity, operability and modulation transfer functions.

512 Pixels Long-Wavelength Infrared (LWIR) Quantum-Dot Infrared Photodetector (QDIP) Imaging Focal Plane Array

A 9-/spl mu/m cutoff 256/spl times/256 hand-held quantum well infrared photodetector (QWIP) camera has been demonstrated. Excellent imagery, with a noise equivalent differential temperature (NE/spl Delta/T) of 26 mK has been achieved. In this paper, we discuss the development of this very sensitive long wavelength infrared (LWIR) camera based on a GaAs/AlGaAs QWIP focal plane array and its performance in quantum efficiency, NE/spl Delta/T, minimum resolvable temperature (MRTD), uniformity, and operability.

1024 × 1024 pixel mid-wavelength and long-wavelength infrared QWIP focal plane arrays for imaging applications

A 9-/spl mu/m cutoff 640/spl times/486 snap-shot quantum well infrared photodetector (QWIP) camera has been demonstrated. The performance of this QWIP camera is reported including indoor and outdoor imaging. The noise equivalent differential temperature (NE/spl Delta/T) of 36 mK has been achieved at 300 K background with f/2 optics. This is in good agreement with expected focal plane array sensitivity due to the practical limitations on charge handling capacity of the multiplexer, read noise, bias voltage, and operating temperature.

9-/spl mu/m cutoff 256/spl times/256 GaAs/Al/sub x/Ga/sub 1-x/As quantum well infrared photodetector hand-held camera

A 9-/spl mu/m cutoff 256/spl times/256 hand-held quantum well infrared photodetector (QWIP) camera has been demonstrated. Excellent imagery, with a noise equivalent differential temperature (NE/spl Delta/T) of 26 mK has been achieved. In this paper, we discuss the development of this very sensitive long wavelength infrared (LWIR) camera based on a GaAs/AlGaAs QWIP focal plane array and its performance in quantum efficiency, NE/spl Delta/T, minimum resolvable temperature (MRTD), uniformity, and operability.

Long-wavelength 640/spl times/486 GaAs-AlGaAs quantum well infrared photodetector snap-shot camera

In this paper, we discuss the development of very sensitive, very long wavelength infrared GaAs/Al/sub x/Ga/sub 1-x/As quantum well infrared photodetectors (QWIPs) based on bound-to-quasi-bound intersubband transition, fabrication of random reflectors for efficient light coupling, and the demonstration of a 15-/spl mu/m cutoff 128/spl times/128 focal plane array imaging camera. Excellent imagery, with a noise equivalent differential temperature (NE/spl Delta/T) of 30 mK has been achieved.

9-{micro}m cutoff 256 x 256 GaAs/Al{sub x}Ga{sub 1{minus}x}As quantum well infrared photodetector hand-held camera

We describe the concept of the submonolayer quantum dot infrared photodetector (SML QDIP) and report experimental device results on long-wavelength infrared detection. An SML QDIP structure was fabricated into megapixel focal plane arrays, which produced clear infrared images up to 80 K. Detectors in the focal plane showed a responsivity peak at 7.8 μm and noise equivalent temperature difference of 33 mK at 70 K.We describe the concept of the submonolayer quantum dot infrared photodetector (SML QDIP) and report experimental device results on long-wavelength infrared detection. An SML QDIP structure was fabricated into megapixel focal plane arrays, which produced clear infrared images up to 80 K. Detectors in the focal plane showed a responsivity peak at 7.8 μm and noise equivalent temperature difference of 33 mK at 70 K.

15-/spl mu/m 128/spl times/128 GaAs/Al/sub x/Ga/sub 1-x/As quantum well infrared photodetector focal plane array camera

A very long wavelength broadband infrared detector, sensitive over a 10–16 μm spectral range, based on GaAs/AlxGa1−xAs quantum wells grown by molecular beam epitaxy, has been demonstrated. Wavelength broadening of Δλ/λp∼42% is observed to be about a 400% increase compared to a typical bound-to-quasibound quantum well infrared photodetector (QWIP). In this device structure, which is different from typical QWIP device structures, two different gain mechanisms associated with photocurrent electrons and dark current electrons were observed and explained. Even with broader response, D*∼1×1010 cmHz/W at T=55 K is comparable to regular QWIPs with similar cutoff wavelengths.

Submonolayer quantum dot infrared photodetector

In this paper, we discuss the development of very sensitive, very long wavelength infrared GaAs/Al/sub x/Ga/sub 1-x/As quantum well infrared photodetectors (QWIPs) based on bound-to-quasi-bound intersubband transition, fabrication of random reflectors for efficient light coupling, and the demonstration of a 15-/spl mu/m cutoff 128/spl times/128 focal plane array imaging camera. Excellent imagery, with a noise equivalent differential temperature (NE/spl Delta/T) of 30 mK has been achieved.