First-principles pseudopotential calculations were used to investigate the atomic structure and energetics of various defects consisting of B and P impurities, and of the effect of P upon B diffusion. In the equilibrium case, it was found that a B-P pair was energetically most stable when the P was situated at a second-nearest neighbor site of B. When excess Si interstitials were generated by implantation, B and P impurities tended to form Is-B-P complexes with self-interstitials, (Is). Here, the P still preferred a second-nearest neighbor site of B; especially at high donor concentrations. By using the nudged elastic band method, the diffusion of B and its energy barrier in the presence of P was examined. It was found that the B diffusion pathways were similar to those reported for the Is-B pair, without P. However, the migration energy for B diffusion from the Is-B-P complex increased by about 0.2eV. The increase in the activation energy, and the formation of the B-P pair which acted as a trap for B diffusion, provided a clue to an understanding of the suppression of B diffusion which was observed in material that was heavily pre-doped with donor impurities.

Atomic Structure of B-Related Defects and B Diffusion in Si Pre-Doped with P Impurities. C.Y.Moon, Y.S.Kim, K.J.Chang: Physical Review B, 2004, 69[8], 085208 (5pp)