Atomic-scale characterization of boron diffusion in silicon

Abstract

By means of density-functional based tight-binding molecular-dynamics (DF-TBMD) simulations, we investigated the diffusion dynamics of boron in crystalline silicon. First, the energetics of single B defects in silicon, given by the present model, has been compared to first-principle results, and a discussion is provided on the overall accuracy of the DF-TBMD parametrization. We then computed the migration energy in the range 900--1500 K, obtaining a value 0.66 eV. By direct analysis of computer-generated trajectories, we show that B diffusion is a self-interstitial assisted process, displaying no kick-out events. Rather, Si--B pairs clearly diffuse through an interstitialcy mechanism. We predict a diffusion pre-exponential factor ${d}_{\mathrm{B}}^{0}=1.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3} {\mathrm{cm}}^{2}/\mathrm{s}.$