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 V₁= (1. 30. 5) eV, which in n-type material can be lowered by ₁= (0. 80. 4) eV due to carrier capture. Both numbers agree well with experiment. Assuming a similar migration path for interstitial silicon the calculated values are V₁ (0. 40. 5) and (2. 00. 4) eV. In addition, the heat of tetrahedral formation of interstitial Si is evaluated to be ₈4. 7 eV.