Structural Relaxation in Metastable Strained-Layer Semiconductors

Abstract

In this paper, the authors attempt to outline the current understanding of structural relaxation in strained-layer semiconductor systems in a manner that is both accessible and easily applied to design of strained-layer device structures. This outline has been based on two primary concepts, the excess stress as the driving force for strain relaxation and a simple description of the material response to the excess stress by means of stability diagrams. Although this approach to strained-layer relaxation provides a useful package, there are many aspects of this area of research that could not be treated because of space limitations. Among these are detailed relaxation models, based on continuum models for plastic flow in bulk semiconductors, which have proven valuable in treating the kinetics of strain relaxation. We have also found that there are many circumstances in which the formulation for excess stress must be altered to reflect other dislocation interactions within the strained-layer structure. Specific examples include interactions between misfit dislocations, which reduce the maximum extent of relaxation, and interaction of dislocations with point defects, which can seriously restrict the initial stages of relaxation.