It was recalled that an experimental characteristic of As diffusion was that the coefficient was independent of the surface concentration, but increased roughly linearly with the electrically active As concentration. From the point of view of the pair diffusion model, this implied that excess vacancies were not generated and that vacancies were in a thermal equilibrium state. Here, As diffusion was studied on the basis of the pair diffusion model, while taking account of a decrease in the quasi-vacancy formation energy. With decreasing quasi-vacancy formation energy, the binding energy between an As atom and a vacancy also decreased. The Fermi level which was deduced from Boltzmann statistics was used. By using published data for the self-diffusion coefficient of vacancies, and the As diffusion coefficient, the experimentally observed As concentration profile could be explained.

M.Yoshida, E.Arai: Japanese Journal of Applied Physics, 1996, 35[1-1A], 44-55