The lattice Monte Carlo method, with parameters gleaned from first-principles calculations, was used to investigate dopant diffusion. In the simulations, vacancy hopping on a Si lattice was biased by changes in system energy, including interactions up to the sixth-nearest neighbor. It was found that vacancy-mediated diffusivity increased markedly above 1020/cm3; in agreement with experimental observations and previous calculations. For very long simulation times, the As diffusivity was reduced due to the formation of AsxV complexes, with clustering being more pronounced at high doping levels. It was found that As2V complexes were mobile and, although they diffused much more slowly than AsV pairs, they appeared to be likely to play a significant role in high-concentration diffusion due to their much higher numbers. Dopant fluxes in a vacancy gradient were also investigated. For dopants like As, where pair diffusion was limited by dissociation to third-nearest neighbor distances, the dopant flux was less than that predicted by pair diffusion models; with a greater difference at higher temperatures. For P-vacancy pairs, whose diffusion was limited by dopant/vacancy exchange, the dopant flux was close to the predictions for pair diffusion.

Lattice Monte Carlo Simulations of Vacancy-Mediated Diffusion and Aggregation using ab-initio Parameters. M.M.Bunea, S.T.Dunham: Materials Research Society Symposium – Proceedings, 1997, 469, 353-8