ABSTRACT
This chapter considers the detector dark current which is of fundamental importance because the dark current related noise commonly limits detector performance. It also considers the photoconductivity of multiple quantum wells structures and explores the differences from the conventional theory of photoconductivity. The chapter discusses the primary noise sources associated with dark current and background photon fluctuation, and the gain associated with the dark current noise. The device operation of photoconductive quantum well infrared photodetectors (QWIPs) is similar to that of conventional semiconductor photoconductors. The distinct feature of QWIPs, in contrast with the conventional intrinsic or extrinsic photoconductors, is the discreteness, i.e., incident photons are only absorbed in discrete quantum wells which are normally much narrow than the inactive barrier regions. Understanding the dark current in QWIPs is one of the most important aspects in optimizing detector performance.
