Chapter 4 - GalnAs(P) based QWIPs on GaAs, InP, and Si substrates for focal plane arrays

Abstract

This chapter opens with the discussion of infrared detectors. Infrared detectors are very important in both civilian and military applications and have been extensively studied. Infrared detectors can be categorized as either thermal detectors or photon detectors. All the real-world applications of the infrared detector are based on thermal imaging using the infrared focal plane array (FPA) camera. An FPA is an optical sensor placed at the focal plane of an optical system such as a camera, spectrometer, or telescope. The quantum well infrared photodetector (QWIP) is a semiconductor infrared photon detector relying on intersubband absorption within either the conduction band (n-type) or the valence band (p-type). Most QWIPs are grown on GaAs (GaAs/A1GaAs heterostructure) and InP (GaInAs/InP heterostructure) substrates. GaAs/A1GaAs QWIPs directly grown on Si have been reported, ss-87 QWIPs directly grown on Si can make use of large-area substrates, with higher thermal conductivity and mechanical strength. The chapter gives a brief review of current Al-free GalnAs (P) QWIPs grown on InP, GaAs, and Si substrates. Device physics, fabrication, and measurement have been described in detail. Infrared QWIP detectors have moved from the laboratory to the thermal imaging market. QWIP research is very active and requires more development to reach the QWIP's full potential. Higher operating temperature and multispectral QWlP cameras are the most straightforward goals. With new processing technology, a much smaller and larger format infrared FPA based on Al-free QWIP structures is likely to be available.