A vacancy-mediated diffusion mechanism was assumed in traditional models of P diffusion in Si. However, recent experiments have suggested that for intrinsic P diffusion in Si, the interstitial-assisted diffusion mechanism predominate. First-principles calculations of P diffusion in Si were performed in order to study interstitial- and vacancy-mediated diffusion mechanisms. Special care was taken with regard to structural minimization, charge-state effects and corrections. Defect formation energies and migration barriers were calculated for various competing P–interstitial diffusion mechanisms, as well as P–vacancy diffusion energetics in different charge states. For P–interstitial diffusion, overall diffusion activation energies of 3.1 to 3.5eV were found for neutral and +1 charge states; in close agreement with experiments under intrinsic conditions. For P–vacancy diffusion, the calculations were in agreement with previous calculations in the neutral case, but suggested that only P+V= plays a role in the heavily doped n region while the interstitial mechanisms may dominate in near-intrinsic regions.

X.Y.Liu, W.Windl, K.M.Beardmore, M.P.Masquelier: Applied Physics Letters, 2003, 82[12], 1839-41