The Lattice Vacancy in Si and Ge

The extended Hückel theory is used to study the electronic structure of the vacancy in Si and Ge. Localized levels associated with the vacancy are found in the forbidden gap near the valence‐band edge. The equilibrium positions of the four neighboring atoms around the vacancy after symmetric relaxation are predicted for the four different charged states of the vacancy. Jahn‐Teller effects are found to he small. The migration energies for vacancies in Si and Ge are also estimated. Results are compared with other calculations and experimental data.