Self-interstitial defect in germanium

Electronic and structural properties of a self-interstitial defect in Ge are studied through first-principles calculations. As in Si, the lowest-energy configuration is the [110] dumbbell. However, the defect in Ce seems to involve four rather than just two atoms, and we propose to call it a kite defect. The formation energy for the interstitial at a hexagonal site is significantly higher in Ce when compared to Si, which may help to explain why in Ge only the vacancy contributes to self-diffusion. An interpretation of recent perturbed angular correlation spectroscopy results is also presented.