Basics and Theory

Abstract

Optical absorption is a fundamental process which is exploited when optical energy is converted into electrical energy. Optoelectronic receivers are based on this energy conversion process. Photodetectors convert optical energy into electrical energy. In this chapter, the most important factors needed for the comprehension of photodetectors will be summarized in a compact form. For a detailed description of the basics of optical absorption, the book [1] can be recommended. Here, emphasis will, of course, be placed on silicon devices. After the collection of the most important optical and optoelectronic definitions, we will summarize the fundamentals of device physics and modeling of solid-state electron devices including photodetectors in a compact form. A detailed review on modeling of solid-state electron devices can be found in [2]. Here, the semiconductor equations with implemented photogeneration and the models for carrier mobility used in device simulators will be listed first. Carrier drift and diffusion as well as their consequences for the speed and the quantum efficiency of photodetectors will be explained. Furthermore, the equivalent circuit of a photodiode will be discussed in order to show further aspects concerning the speed of photoreceivers.