The role which was played by surface-step formation in misfit dislocation nucleation and critical-thickness effects in thin-film semiconductor heterostructures was studied. On the basis of an atomistic model, it was shown that the energy change due to step formation was negative or positive; depending upon the sign of the misfit. The step formation energy could even be negative for a compressive misfit stress in the heterolayer, while it was definitely positive for a tensile misfit stress. This conclusion contrasted with the classical model; where the step-energy was always positive and was independent of the sign of the misfit. The step-formation energy affected the critical thickness, and the energy barrier for dislocation nucleation. By using a simple atomistic simulation, It was shown that the critical thickness depended upon the sign of the misfit. For example, it changed from 4nm for Ge films on (100) Si substrates to 6nm for Si films on (100) Ge substrates; both having the same misfit.

Role of Surface Step on Misfit Dislocation Nucleation and Critical Thickness in Semiconductor Heterostructures. M.Ichimura, J.Narayan: Materials Science and Engineering B, 1995, 31[3], 299-303