Critical thickness calculations for InGaN/GaN

A model based on the overall energy balance is used to calculate the critical thickness for an InGaN epitaxial layer on a GaN substrate. The critical thickness values as a function of the indium content are found to be lower than values predicted by models proposed by Fischer or People and Bean. We also used the energy balance model to estimate the effect of the hexagonal symmetry of wurtzite materials on the critical thickness; this results in reduction of the critical thickness by as much as 20% of its corresponding isotropic value. From the small amount of experimental data available we conclude that the energy balance model is more appropriate for describing the critical thickness of the InGaN/GaN material system than the models developed by Fischer or People and Bean.