Semiconductor Photodetectors

This chapter describes the operating principles of photoconductive and photovoltaic detectors based on III–V semiconductors. The electrical characteristics of both photodiodes and majority carrier barrier structures are discussed starting with the diffusion equation. The chapter outlines the figures of merit used to evaluate the performance of infrared photodetectors including the responsivity, dark current density, and normalized detectivity. It discusses bulk-like and type II superlattice photodetectors and how the multistage arrangement of interband cascade detectors (ICDs) can reduce the dark current density at the expense of a lower responsivity. Detectors that employ intersubband optical transitions, namely, quantum-well infrared photodetectors and quantum cascade detectors, are also discussed. The chapter considers how the dark-current density can be suppressed in resonant-cavity and thin waveguide-based detectors. It concludes with a discussion of the requirements for high-speed operation and an overview of novel types of detectors that draw their inspiration from III–V semiconductor devices.