Influence of surface steps on glide of threading dislocations during layer growth

We discuss the relaxation of coherency stresses by glide of threading dislocations in a layer that is growing coherently on a substrate. Glide of threading dislocations becomes energetically favorable when the thickness of the layer exceeds a critical value, hc. Predicted values of hc are often less than indicated by experimental observations. We show that the energy associated with the creation or removal of steps on the surface of a growing layer is important in determining the hc associated with glide of threading dislocations.