It was noted that the binding energy between a vacancy and a P atom was large in Si. Therefore, the pair diffusion model and a decrease in quasi-vacancy formation energy with increasing P concentration could be used in the study of P diffusion in Si. The anomalous diffusion of P consisted of 2 parts: a tail and a plateau. The tail was explained by using the pair diffusion model, in that the tail was attributed to the presence of excess vacancies. The generation of such vacancies was caused by the dissociation of E centers, and was a characteristic of the pair diffusion model. The plateau was explained mathematically, using the pair diffusion model, by taking account of the decrease in quasi-vacancy formation energy. The main point which was made here was that, with a decrease in quasi-vacancy formation energy, the binding energy also decreased and the pair diffusion model became identical to the ordinary diffusion model; in which excess vacancies were not generated. It was emphasized that a large value of the effective P diffusion coefficient at the plateau was not anomalous, but normal.

M.Yoshida: Materials Science Forum, 1995, 196-201, 1595-600