III-V infrared research at the Jet Propulsion Laboratory

Abstract

Jet Propulsion Laboratory is actively developing the III-V based infrared detector and focal plane arrays (FPAs) for NASA, DoD, and commercial applications. Currently, we are working on multi-band Quantum Well Infrared Photodetectors (QWIPs), Superlattice detectors, 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 report the first demonstration of the megapixel-simultaneously-readable and pixel-co-registered dual-band QWIP focal plane array (FPA). In addition, we will present the latest advances in QDIPs and Superlattice infrared detectors at the Jet Propulsion Laboratory.Keywords: infrared detectors, infrared imaging, quantum well devices QUANTUM WELL INFRARED PHOTODETECTOR (QWIP)Single-band Quantum well infrared photodetectors (QWIPs) are well known for their ease of fabrication, ruggedness, pixel-to-pixel uniformity and high pixel operability [1]. QWIP is based on a resonant absorption between ground state and a quasi-continuum state. The spectral response of QWIPs are inherently narrow-band and the typical full-width at half-maximum (FWHM) is about 10% of the peak wavelength. This makes it suitable for fabrication of negligible optical cross-talk dual-band detector arrays.There are many applications that require mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) dual-band focal plane arrays (FPAs). For example, a dual-band FPA camera would provide the accurate temperature [2] of a target with unknown emissivity which is extremely important to the process of identifying objects based on their surface temperature. Dual-band infrared FPAs can also play many important roles in Earth and planetary remote sensing, astronomy, etc. Furthermore, monolithically integrated pixel co-located simultaneously readable dual-band FPAs eliminate the beam splitters, filters, moving filter wheels, and rigorous optical alignment requirements imposed on dual-band systems based on two separate single-band FPAs or a broad-band FPA system with filters. Dual-band FPAs also reduce the mass, volume, and power requirements of dual-band systems. Due to the inherent properties such as narrow-band response, wavelength tailorability, and stability (i.e., low 1/f noise) associated with GaAs based QWIPs [1], it is an appropriate detector choice for large format dual-band infrared FPAs. DUAL-BAND QWIP DEVICEAs shown in Fig. 1, our dual-band FPA is based on two different types of (i.e., MWIR and LWIR) QWIP devices separated by a 0.5 μm thick, heavily doped, n-type GaAs layer. One can stack the MWIR and LWIR multi-quantumwell (MQW) structures in different ways. The device structure shown in Fig. 1(a) is commonly used and described in reference [3]. Fig. 1 (b) -(c) are novel and these structures have two heavily doped GaAs contact layers between MWIR and LWIR MQW regions and an undoped AlGaAs layer embedded between these two GaAs contact layers.