Jean Nguyen

A high-performance long wavelength superlattice complementary barrier infrared detector

We describe a long wavelength infrared detector where an InAs/GaSb superlattice absorber is surrounded by a pair of electron-blocking and hole-blocking unipolar barriers. A 9.9 μm cutoff device without antireflection coating based on this complementary barrier infrared detector design exhibits a responsivity of 1.5 A/W and a dark current density of 0.99×10−5 A/cm2 at 77 K under 0.2 V bias. The detector reaches 300 K background limited infrared photodetection (BLIP) operation at 87 K, with a black-body BLIP D∗ value of 1.1×1011 cm Hz1/2/W for f/2 optics under 0.2 V bias.

Type-II Superlattice Infrared Detectors

Publisher Summary This chapter provides an overview of type-II superlattice infrared detectors. The type-II InAs/GaSb superlattices have several fundamental properties that make them suitable for infrared detection: (1) their band gaps can be made arbitrarily small by design, (2) they are more immune to band-to-band tunneling compared with bulk material, (3) the judicious use of strain in type-II InAs/GaInSb strained layer superlattice (SLS) can enhance its absorption strength over that of the type-II InAs/GaSb superlattice to a level comparable with HgVdTe (MCT), and (4) type-II InAs/Ga(In)Sb superlattices also reduce Auger recombination. In addition, the dark current characteristics of type-II superlattice-based single element long-wavelength infrared (LWIR) detectors are currently approaching state-of-the-art MCT detector. Noise measurements highlight the need for surface leakage suppression, which can be tackled by improved etching, passivation, and device design. The chapter also describes the principles behind advanced superlattice infrared detectors based on heterostructure designs. It also explores some aspects of device fabrication and characterization.

Demonstration of Megapixel Dual-Band QWIP Focal Plane Array

Quantum well infrared photodetectors (QWIPs) are well known for their stability, high pixel-pixel uniformity and high pixel operability which are quintessential parameters for large area imaging arrays. In this paper we report the first demonstration of the megapixel-simultaneously-readable and pixel-co-registered dual-band QWIP focal plane array (FPA). The dual-band QWIP device was developed by stacking two multi-quantum-well stacks tuned to absorb two different infrared wavelengths. The full width at half maximum (FWHM) of the midwave infrared (MWIR) band extends from 4.4-5.1 ¿m and FWHM of the long-wave infrared (LWIR) band extends from 7.8-8.8 ¿m. Dual-band QWIP detector arrays were hybridized with direct injection 30 ¿m pixel pitch megapixel dual-band simultaneously readable CMOS read out integrated circuits using the indium bump hybridization technique. The initial dual-band megapixel QWIP FPAs were cooled to 68 K operating temperature. The preliminary data taken from the first megapixel QWIP FPA has shown system NE¿T of 27 and 40 mK for MWIR and LWIR bands, respectively.

Gain and noise of high-performance long wavelength superlattice infrared detectors

We experimentally investigate the noise and gain of high-performance long-wavelength superlattice (SL) infrared photodetectors. We compare a recently demonstrated SL heterodiode, which exhibits an electrical gain much larger than unity, with a SL photodetector without gain to show that the electrical gain in these devices originates from the device structure rather than from the SL absorber. We directly measure the noise spectra of a high performance SL, and show that 1/f noise is not intrinsically present in these structures. However, we find that a very large extraneous frequency-dependent noise can be generated by side-wall leakage currents. Analysis of the noise and gain indicate that the exact dependence of the shot noise on the dark current in these SL heterodiodes can be different from that in the diffusion-limited diode homojunction.

Demonstration of a 1024

We describe the demonstration of a 1024 × 1024 pixel long-wavelength infrared focal plane array based on an InAs-GaSb superlattice absorber surrounded by an electron-blocking and a hole-blocking unipolar barrier. An 11.5-μm cutoff focal plane without antireflection coating based on this complementary barrier infrared detector design has yielded noise equivalent differential temperature of 53 mK at operating temperature of 80 K, with 300 K background and f/2 cold-stop.

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We demonstrate a long wavelength type-II superlattice (T2SL) complementary barrier infrared detector (CBIRD) with a double broken-gap junction bottom contact structure designed to reduce material growth demands without diminishing performance. Simulation suggests generation-recombination dark current suppression is the result of placing the electrical junction in the wide-gap hole barrier region, away from the metallurgical hole-barrier/absorber heterojunction. The lower turn-on bias of the modified CBIRD is explained in terms of junction properties. We suggest that minority carrier exclusion and extraction effects are partially responsible for the observed low diffusion-limited CBIRD dark current despite short T2SL minority carrier lifetimes.

1024 Pixel InAs–GaSb Superlattice Focal Plane Array

Surface leakage reduction has been achieved using BCl3/Cl2/CH4/H2/Ar inductively coupled plasma dry etching for pixel isolation of high performance long-wave infrared superlattice detectors. The leakage has been minimized by effectively increasing the surface resistivity by more than 7.4 times and decreasing the surface state density by more than 3.8 times. Through altering the etch mechanism, the dark current density was reduced by more than two orders of magnitude where a dark current of 1.01×10−5 A/cm2 at 200 mV was achieved at T=77 K for a 10.3 μm detector with a peak quantum efficiency value of 30% (without antireflection coating).

Exclusion, extraction, and junction placement effects in the complementary barrier infrared detector

Long-wavelength complementary barrier infrared detector (CBIRD) based on III-V material is hybridized to recently designed and fabricated 320 × 256 pixel format two-color read-out integrated circuit. The n-type CBIRD is characterized in terms of performance and thermal stability. This paper reports on the measured dark current density, noise equivalent difference temperature, quantum efficiency, responsivity, minimum resolvable difference temperature, and modulation transfer function.

Low dark current long-wave infrared InAs/GaSb superlattice detectors

The nearly lattice-matched InAs/GaSb/AlSb (antimonide) material system offers tremendous flexibility in realizing high-performance infrared detectors. Antimonide-based alloy and superlattice infrared absorbers can be customized to have cutoff wavelengths ranging from the short wave infrared (SWIR) to the very long wave infrared (VLWIR). They can be used in constructing sophisticated heterostructures to enable advanced infrared photodetector designs. In particular, they facilitate the construction of unipolar barriers, which can block one carrier type but allow the unimpeded flow of the other. Unipolar barriers are used to implement the barrier infra-red detector (BIRD) design for increasing the collection efficiency of photo-generated carriers, and reducing dark current generation without impeding photocurrent flow. We report our recent efforts in achieving state-of-the-art performance in antimonide alloy and superlattice based infrared photodetectors using the BIRD architecture. Specifically, we report a 10 μm cutoff superlattice device based on a complementary barrier infrared detector (CBIRD) design. The detector, without antireflection coating or passivation, exhibits a responsivity of 1.5 A/W and a dark current density of 1×10-5 A/cm2 at 77K under 0.2 V bias. It reaches 300 K background limited infrared photodetection (BLIP) operation at 87 K, with a blackbody BLIP D* value of 1.1×1011 cm-Hz1/2/W for f/2 optics under 0.2 V bias.

Performance of a 1/4 VGA Format Long-Wavelength Infrared Antimonides-Based Superlattice Focal Plane Array

Jet Propulsion Laboratory is actively developing the III-V based infrared detector and focal plane arrays (FPAs) for remote sensing and imaging applications. Currently, we are working on Superlattice detectors, multi-band Quantum Well Infrared Photodetectors (QWIPs), and Quantum Dot Infrared Photodetector (QDIPs) technologies suitable for high pixel-pixel uniformity and high pixel operability large area imaging arrays. In this paper, we will discuss the demonstration of long-wavelength 1Kx1K QDIP FPA, 1Kx1K QWIP FPA, the first demonstration of the megapixelsimultaneously- readable and pixel-co-registered dual-band QWIP FPA, and demonstration of the first mid-wave and long-wave 1Kx1K superlattice FPA. In addition, we will discuss the advantages of III-V material system in the context of large format infrared FPAs.