Equations of state and a tight-binding model for strained layers: Application to a ZnSe-GaAs epilayer.

Abstract

We have studied the elastic and electronic properties of a semiconductor of cubic symmetry simultaneously subjected to a biaxial strain and a high hydrostatic pressure. Owing to the breakdown of the linear Hooke's law at high pressures, we have developed a nonlinear elastic model to describe this experimental situation. Our model is in accordance with Murnaghan's equation of state for hydrostatic pressure. It takes into account the significant pressure variation of the elastic stiffness constants in the high-pressure range. Electronic properties are obtained through a 20-band empirical tight-binding method using the atomic positions calculated from the nonlinear elastic model. The method is applied to a high-pressure experiment in a ZnSe epilayer biaxially strained on a GaAs substrate. We calculate the variation under high pressure of the electronic transitions in that system. Our approach gives satisfactory results and enables us to analyze the anomalous behavior of the experimental transitions in that system in terms of weak anisotropic components of the hydrostatic pressure applied in the diamond-anvil cell.