QWIP and MCT for Long Wavelength and Multicolor Focal Plane Array Applications

Infrared (IR) sensor technology is critical to all phases of ballistic missile defense. Traditionally, material systems such as indium antimonide (InSb), platinum silicide (PtSi), mercury cadmium telluride (MCT), and arsenic doped silicon (Si: As) have dominated IR detection. Improvement in surveillance sensors and interceptor seekers requires large, highly uniform, and multicolor (or multispectral) IR focal plane arrays involving mid-wave (MW), long-wave (LW), and very-long-wave (VLW) IR regions. Among the competing technologies are quantum-well infrared photodetectors (QWIPs) based on lattice-matched GaAs/AlGaAs and strained layer InGaAs/AlGaAs material systems. Even though QWIP cannot compete with MCT at the single device level (considering the quantum efficiency and D*), it has potential advantages over MCT for LW and VLW focal plane array applications in terms of the array size, uniformity, operability, yield, reliability, and cost effectiveness. QWIPs are especially promising for VLWIR at low temperature operation, and when simultaneous multicolor detection with a single focal plane array is desired. Operating a VLWIR focal plane array at low background is a challenge to both MCT and QWIP, while QWIP has more potential to be realized due to its good properties at low temperatures. In this paper, I discuss cooled IR technology with an emphasis on QWIP and MCT. I give details concerning device physics, material growth, device fabrication, device performance, and cost effectiveness for LWIR, VLWIR, and multicolor applications.