The results of theoretical analysis of the process of diffusion of covalently bonded atoms (interstitial oxygen atoms) in Si1-xGex alloys were presented. The diffusion coefficient (activation energy and pre-exponential factor) was calculated by means of quantum-chemical simulations and the dependences of the activation energy and pre-exponential factor on Ge atoms concentration (x) were analyzed with the use of the percolation theory. It was shown that a significant decrease in the diffusion coefficient of interstitial oxygen atoms in Si1-xGex (x<0.05) compared to the value in pure silicon was caused not only by changes in activation energy but also by a decrease of the pre-exponential factor. The alloy-induced decrease in the pre-exponential factor was associated with removal of the degeneracy of the number of equivalent diffusion paths. The dependences obtained described well experimentally observed changes in the diffusion coefficient of interstitial oxygen atoms and in the formation rate of oxygen-related thermal donors in Si1-xGex alloys.

Quantumchemical Simulation of Diffusion in Alloys: Diffusion of Interstitial Oxygen Atoms in Si1-xGex. V.Gusakov: Physica Status Solidi C, 2011, 8[3], 682–5