Analysis of the shortcomings of the Matthews-Blakeslee theory of critical thickness at higher strains

The Matthews-Blakeslee equilibrium theory provides predictions of the critical thickness of a strained heteroepitaxial layer as a function of misfit strain and material constants. At low strains the prediction is double Valued with one value producing a physically reasonable result for the critical thickness. At higher strains, no prediction is provided at all. It is shown that these features arise from a particular approximation which increases in importance for larger strains and hence for reduced critical layer thickness. A correction is proposed which lessens the influence of this approximation and which provides a single-valued prediction for all layer thicknesses, thus extending the useful range of applicability of the Matthews-Blakeslee theory.