Migration of interstitials in silicon

We calculate total configurational energies for interstitial aluminum and silicon in silicon. The calculations, based on the self-consistent Green's-function technique, are done for a selective migration path along the "empty" channel in crystalline silicon. Short- and long-range structural distortions are found to be sizable and strongly varying along the migration path. Carrier capture is possible along the migration path, resulting in a drastic dependence of the migration barrier on the nominal charge-state of the defect. For aluminum migration in $p$-type silicon we find a barrier of $V_B=(1.3\mathrm{}\pm 0.5)$ eV, which in $n$-type material can be lowered by ${\Delta V}_B=(0.8\mathrm{}\pm 0.4)$ eV due to carrier capture. Both numbers agree well with experiment. Assuming a similar migration path for interstitial silicon the calculated values are $V_B\approx (0.4\mathrm{}\pm 0.5)$ and (2.0±0.4) eV. In addition, the heat of tetrahedral formation of interstitial Si is evaluated to be ${\Delta H}_I\approx 4.7$ eV.