Kinetic lattice Monte Carlo simulations were made of substitutional As diffusion in Si mediated by lattice vacancies. Large systems were considered, with 1000 dopant atoms and long-range ab initio interactions, to the 18th nearest lattice neighbor, and the diffusivity of each defect species over time was calculated. The concentration of vacancies was greater than equilibrium concentrations in order to simulate conditions shortly after ion implantation. A previously unreported time dependence in the applicability of the pair diffusion model, even at low temperatures, was demonstrated. Additionally, long-range interactions were shown to be of critical importance in kinetic lattice Monte Carlo simulations; when shorter interaction ranged were considered, only clusters composed entirely of vacancies formed. An increase in As diffusivity for As concentrations up to 1019/cm3 was observed, along with a decrease in As diffusivity for higher As concentrations, due to the formation of As-dominated clusters. Finally, the effect of vacancy concentration on diffusivity and clustering was studied, and increasing vacancy concentration was found to lead to a greater number of clusters, more defects per cluster, and a greater vacancy fraction within the clusters.

Vacancy-Assisted Arsenic Diffusion and Time-Dependent Clustering Effects in Silicon. B.P.Haley, N.Grønbech-Jensen: Physical Review B, 2005, 71[19], 195203 (8pp)