The nucleation of misfit dislocations in Ge/(001)Si heterostructures was investigated theoretically by using an atomistic model that was based upon the Stillinger-Weber potential. Both 60 and 90 dislocations were considered, and the energy was calculated as a function of the distance of the dislocations from the free surface in a thin-film heterostructure. The critical thicknesses for dislocation nucleation, which were obtained from the atomistic simulations, were larger than those predicted by a previous continuum analysis. This difference was attributed mainly to the core energy of the dislocations. The activation barrier to dislocation nucleation from the surface was estimated from the variation in energy with the distance of a dislocation from the surface. The calculated activation energy was much higher than the thermal energy at normal growth temperatures. The interaction between two 60 dislocations, and the formation of a 90 dislocation at the interface via a dislocation reaction mechanism, were also considered.

M.Ichimura, J.Narayan: Philosophical Magazine A, 1995, 72[2], 281-95