Introduction

Heterostructures are the building blocks of many of the most advanced semiconductor devices presently being developed and produced. They are essential elements of the highest-performance optical sources and detectors [1,2], and are being employed increasingly in high-speed and high-frequency digital and analog devices [3,4,5]. The usefulness of heterostructures is that they offer precise control over the states and motions of charge carriers in semiconductors.

For the purposes of the present work, a heterostructure is defined as a semiconductor structure in which the chemical composition changes with position. The simplest heterostructure consists of a single heterojunction, which is an interface within a semiconductor crystal across which the chemical composition changes. Examples include junctions between GaSb and InAs semiconductors, junctions between GaAs and AlGaAs solid solutions, and junctions between Si and GeSi alloys. Most devices and experimental samples contain more than one heterojunction, and are thus more properly described by the more general term heterostructure.

• Atomic Structure of Heterojunctions