Point defect diffusion in Si and SiGe revisited through atomistic simulations

In this paper, we revisit the theory of point defect diffusion in silicon using atomistic calculations. In the first part, we discuss on the concept of effective migration energy. We use it to analyze the apparent discrepancies found in the literature on vacancy migration. Our calculations show that the diffusion might be non-Arrhenian depending on the temperature range and on the vacancy concentration. The model is generalized and further extended to a class of mechanism, illustrated by the Ge diffusion in silicon through interstitial mechanisms. In the second part, we give an overview on the experimental determination of strain-enhanced vacancy diffusion using a coherent definition for the strain derivative (Q′Q′) of the activation energy. Based on ab initio   calculations, we predict that Q′Q′ in pure silicon is highly non-linear due to a broken degeneracy of the split-vacancy configuration. Finally, we report on the suppression of the vacancy-oxygen complex formation in Czochralski silicon using point defect engineering.