In semiconductor heteroepitaxy, misfit strain leads to island formation. Tremendous effort has been devoted to studying these islands, because of their promise as "self-assembled quantum dots". However, one aspect of the growth has been largely ignored theoretically: there is always some intermixing between the deposited material and the substrate layer. Intermixing occurs via surface diffusion, even when bulk diffusion is negligible. This talk describes a "multi-scale" continuum approach to this problem, and its application in direct simulations of heteroepitaxial growth and formation of nanoscale structures. The results show that alloy intermixing via surface diffusion is crucial in explaining several puzzling features of heteroepitaxial growth.
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