Interstitial oxygen in Si and Si/sub 1-x/Ge/sub x

The equilibrium geometry, phonon spectra, and electronic structures of O interstitial defect in Si and Si/sub 1-x/Ge/sub x/ are calculated using ab initio plane-wave density-functional method. The effect of O, Si, and Ge isotopes on the phonon spectra is also investigated and found in good agreement with the available experimental data. Our calculations also support experimental evidence that in a Ge doped Si crystal an oxygen atom prefers to occupy a position between two Si atoms, rather than between Si and Ge atoms. (31 References).