Dislocation Mechanisms of Relaxation in Strained Epitaxial Films

Abstract

Advances in the methods of deposition and characterization of crystalline films of submicron thickness have been dramatic over the past two decades. A principal motivation for development of this technology has been the potential for use of thin film semiconductor materials in electronic and optoelectronic devices. The main function of these devices is to control transport of electrons in a way which permits high spatial density, and in which the carriers are highly mobile, that is, they show fast response with little power consumption. Spatial control of mobile electrons can be facilitated by combining materials, forming a material heterostructure, with one or more of these materials being a thin film. Carrier confinement is enforced by a difference in energy band structure across the interface acting as a barrier. The exploitation of this physical effect in device design is called bandgap engineering. A great deal of attention has been focused on film/substrate systems involving the III-V compounds (InGaAs/GaAs, for example), as well as on II-VI compounds for optical applications (ZnSe/GaAs, for example). Current efforts are also directed toward SiGe/Si and GaAs/Si systems to exploit well-developed silicon device technology.