New model for the thickness and mismatch dependencies of threading dislocation densities in mismatched heteroepitaxial layers

Abstract

A new model is proposed for the thickness dependence of the threading dislocation densities in mismatched heteroepitaxial semiconductor layers. This ‘‘glide model’’ has been developed based on the premise that dislocations establish mechanical equilibrium between the line tension in their misfit segments and the glide force experienced by their threading segments. The glide model correctly predicts the inverse relationship between the film thickness and the dislocation density in mismatched heteroepitaxial layers which are much thicker than the critical layer thickness. It also predicts the weak dependence of the dislocation density on the lattice mismatch. The quantitative results of the glide model are in fair agreement with published experimental results although no unknown or adjustable parameters have been incorporated.