First-principles study of interaction of as-vacancy and ring mechanism of diffusion under presence of Ge in Si

We performed first-principles calculation to study the interaction of As-vacancy and ring mechanism of diffusion under presence of Ge in Si in neutral and positively charged state respectively, in which it is found that the vacancy barrier decreased substantially when it hops around the ring. We believe it indicates that existence of As atom can lower the vacancy migration barrier. The vacancy migration barrier also decreased with existence of Ge atom in vicinity. We also calculate As-vacancy ring mechanism in the crystalline Ge. It is found that the formation energy of the vacancy and migration barrier was obviously smaller than that in crystalline Si. All these results support the suggestion that As diffusion can be enhance with presence of Ge, and provide physical insight of As diffusion in Si1-xGex.