Evaluation of dislocation energy in thin films

A procedure is proposed to calculate the energy of a misfit dislocation at the interface of a film with a finite thickness and a substrate with semi-infinite thickness when modelled anisotropically and with different elastic properties. The results are compared with the treatments derived by Steeds, Willis, Jain and Bullough, and Freund. The new formula is used to calculate the equilibrium critical thickness for AlGaN/GaN, InGaN/GaN and SiGe/Si heterostructures. A comparison with experimental data from the literature shows good agreement. In contrast to other models, application of the new formula for dislocation energy yields smaller critical thickness for the onset of the misfit dislocations.