A theoretical modelling of the O diffusivity in Si and Ge crystals both at normal and high hydrostatic pressure was carried out using molecular mechanics, semi-empirical and ab initio methods. It was established that the diffusion process of an interstitial O atom (Oi) was controlled by the optimum configuration of three Si (Ge) atoms nearest to Oi. The calculated values of the activation energy ΔEa(Si) = 2.59eV, ΔEa(Ge) = 2.05eV and pre-exponential factor D0(Si) = 0.28cm2/s, D0(Ge) = 0.39cm2/s were in good agreement with experimental ones and for the first time described perfectly the experimental temperature dependence of the Oi diffusion constant in Si crystals (T = 350–1200C). Hydrostatic pressures (P≤80kbar) resulted in a linear decrease, in the diffusion barrier, of –0.00438eV/kbar for Si crystals. The calculated pressure dependence of Oi diffusivity in Si crystals agrees well with the pressure-enhanced initial growth of O-related thermal donors.

Unified Model of Diffusion of Interstitial Oxygen in Silicon and Germanium Crystals. V.Gusakov: Journal of Physics - Condensed Matter, 2005, 17[22], S2285-91