Overview

The optical properties of any material are the result of photon interactions with the constituents of the material. The aim of this chapter is to describe photon interactions with semiconductor materials, including low-dimensional systems, that lead to effects that are the basis for many technologies, such as detectors, emitters, optical communications, display panels, and optical oscillators. The interaction of photons with electrons in semiconductor materials is most important and gives rise to many phenomena. Electrons in semiconductor materials can absorb photons and be excited from the valence band to the conduction band. This is called the interband transition. The inverse of this process occurs when electrons decay from a higher energy level, such as a conduction band, to a lower energy level, such as a valence band, and photons are emitted. This is the basis for light-emitting diodes (LEDs) and laser diodes. Electrons can absorb photons and be excited from one state to another within a particular band, such as a conduction band. This transition is called an intraband transition. In low-dimensional systems, such as quantum wells, wires, and dots, electrons can be excited by photons and jump from one confined energy level to another. When the electrons are excited from a bound state to another bound state in the conduction band of a quantum well, for example, the transition is called an intersubband transition. These terminologies are also applied to heavy or light holes in semiconductors. These transitions are illustrated for a bulk material in...