Migration of interstitials in silicon

Abstract

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 ${V}_{B}=(1.3\ifmmode\pm\else\textpm\fi{}0.5)$ eV, which in $n$-type material can be lowered by ${\ensuremath{\Delta}V}_{B}=(0.8\ifmmode\pm\else\textpm\fi{}0.4)$ eV due to carrier capture. Both numbers agree well with experiment. Assuming a similar migration path for interstitial silicon the calculated values are ${V}_{B}\ensuremath{\approx}(0.4\ifmmode\pm\else\textpm\fi{}0.5)$ and (2.0\ifmmode\pm\else\textpm\fi{}0.4) eV. In addition, the heat of tetrahedral formation of interstitial Si is evaluated to be ${\ensuremath{\Delta}H}_{I}\ensuremath{\approx}4.7$ eV.