Theoretical calculations showed that the defect properties of undoped and As-doped (100) surfaces were completely different. Large atomic relaxations around vacancies near to the (100) surface caused chemical re-bonding and defect healing that greatly lowered their formation energies. Passivation of the surface by a monolayer of As led to a substantial structural rigidity in the near-surface region. This reduced atomic relaxations and increased vacancy formation energies to high values; thus inhibiting vacancy-mediated processes near to the surface. The formation energies of Si interstitials near to the As-passivated surface were significantly lower than those of vacancies, which favoured an interstitial mode of As incorporation into the bulk during in-diffusion. The results explained the observed uniformity of As-doped Si(100) surfaces, and the high level of electrical activation of in-diffused As.

Defect Energetics and Impurity Incorporation Mechanisms at the Arsenic-Passivated Si(100) Surface M.Ramamoorthy, E.L.Briggs, J.Bernholc: Physical Review B, 1999, 60[11], 8178-84