The structure and electrical properties of SnV2, Sn2V, and Sn2V2 complexes in Si were investigated using first-principles cluster and super-cell methods. The formation of SnV2 and Sn2V2 was found to be energetically favorable, in agreement with the experimental results. All the tin-vacancy defects were found to possess deep donor and acceptor levels, although the number of the gap states decreases with increasing size of the defect. The diffusion of tin in Si was considered and the mechanism found to be distinct from the diffusion of group V shallow donors. In contrast with these, the Sn-V interaction was found to extend only to the third-nearest neighbor distance. This implies that the activation energy for Sn diffusion via vacancies should be nearly the same as self-diffusion by this mechanism. An activation energy of 3.5eV was found which was close to some experimental findings, but considerably lower than others.

Tin-Vacancy Complexes in Silicon. M.Kaukonen, R.Jones, S.Öberg, P.R.Briddon: Physical Review B, 2001, 64[24], 245213 (9pp)