The dynamics of island formation on strained epitaxial films is investigated using the system formed by InAs on InP. Island shape, size, and spatial distribution are determined by surface atom diffusion that is modified by the presence of steps and/or corrugations on the surface. Different step characteristics-type and density-are shown to strongly affect the islanding process. By controlling the morphology of the underlying InP film we were able to achieve InAs/InP structures with periodic spatial distribution in one single step of growth.57191250112505