The effective diffusivity of substitutional impurities was considered with regard to point defects. It was noted that 4 basic reactions, which involved interstitial and vacancy contributions, had to be considered in order to derive a general formula for the effective diffusion coefficient. The model was fitted to data on As diffusion under nitridation conditions, and was found to give very good agreement. On the basis of the results, it was deduced that the As diffused mainly via a vacancy mechanism; but with a non-negligible partial interstitial contribution. It was also observed that, under these conditions, the point defect concentrations were a complicated function of the observed P and Sb diffusivities. The general behavior of the dopant diffusivities as a function of point defect concentration was also studied. It was concluded that the recombination of point defects, mediated by dopant pairs, was important over a wide range of point defect concentrations.

E.Vandenbossche, B.Baccus: Journal of Applied Physics, 1992, 72[2], 447-53