It was recalled that, when considering dopant diffusion processes at very high concentrations (close to the solubility limit) it was essential to take account of the fact that the number of substitutional sites which was accessible to additional donors and acceptors was decreasing, or equal to zero, when their concentration approached or exceeded the solubility limit. It was found that this resulted in greatly enhanced diffusion at dopant concentrations which were comparable to the solubility limit. In the case of simple diffusion mechanisms, it was possible to derive an analytical expression, for the effective diffusion coefficient, which depended upon the dopant concentration.

E.Antoncik: Journal of the Electrochemical Society, 1994, 141[12], 3593-5