Strain effect on self-diffusion in silicon: Numerical study

Abstract

We present here a numerical study of the self-diffusion mechanisms in silicon using a semiempirical Stillinger-Weber potential to calculate formation and migration energies and entropies. We find that self-diffusion in bulk Si is mediated by vacancies at low temperature, but that interstitials play a more and more important role when temperature increases, in agreement with recent experimental data. This behavior is shown to strongly evolve under biaxial strain $(ϵ)$ which simulates the effect of epitaxial growth of a Si thin film. Our methodology allows us to classify vacancy vs interstitial self-diffusion within a $(T,ϵ)$ diagram, which reveals a transition from vacancy toward interstitial diffusion at low temperature beyond a critical tensile strain which corresponds to Si/Ge size mismatch.