An extensive numerical study was made of the basic mechanisms that described Ge diffusion in Si mediated by point defects. This diffusion could be created by vacancies, interstitial atoms or fourfold coordinated defects. All of the energies and elementary barriers were precisely determined by means of ab initio calculations. The results for vacancies were compared with recently published values. The complex interstitial landscape was systematized and the key role played by the hexagonal location was stressed as a halfway stable state between 2, more stable, dumb-bell [110] states. Finally, the mechanism of a concerted exchange linking 2 fourfold coordinated defects was fully calculated. Its activation energy was higher than that for interstitial or vacancy mediated movements.

Germanium Diffusion Mechanisms in Silicon from First Principles. D.Caliste, P.Pochet, T.Deutsch, F.Lançon: Physical Review B, 2007, 75[12], 125203