Activation Volume for Boron Diffusion in Silicon and Implications for Strained Films

The diffusivity of B in Si is enhanced by pressure, characterized by an activation volume of -0.17 +- 0.01 times the atomic volume OMEGA, which is close to the formation volume of the self-interstitial determined by atomistic calculations. The results for hydrostatic pressure are used to make predictions for the effect of biaxial strain on diffusion. Assuming an interstitial-based mechanism and a range of values for the anisotropy in the migration volume, comparison is made between our results, the atomistic calculations, and the measured dependence of B diffusion on biaxial strain. We find a qualitative consistency for an interstitial-based mechanism with the measured strain effect on diffusion in Si-Ge alloys, but not with the measured strain effect in pure Si. Possible origins of this discrepancy are discussed.