Ultra-fast diffusion mechanism of the late 3d transition metal impurities in silicon

Based upon ab initio electronic structure calculations with super-cells and an FLAPW method, we discuss the mechanism of the ultra-fast diffusion and the reduction of the migration barriers of the late 3d transition atom impurities of Co, Ni and Cu in silicon. The reduction mechanism of the migration barriers of the late 3d transition metal impurities is due to the pseudo-Jahn-Teller interaction, in which the six-fold-coordinated bonds are formed at the interstitial D-3d symmetry site and the energy gain by these bonds overcomes that of the four-fold-coordinated bonds at the tetrahedral T-d interstitial site. For Sc, Ti, V, Cr, Mn and Fe impurities in silicon, the Td interstitial site is more stable than the D-3d site, however, for Co, Ni and Cu impurities, the D-3d interstitial site becomes more stable than the T-d interstitial site. Calculated migration barriers are in reasonably good agreement with the experimental data. We discuss the systematic variation of the chemical trend of the migration barrier of 3d transition metal impurities in silicon based upon the calculation. (C) 2001 Elsevier Science B.V. All rights reserved.