Self-consistent electronic states for reconstructed Si vacancy models

Vacancy states in Si are investigated using a recently developed self-consistent pseudopotential technique. Three different structural models (ideal and two reconstructions) for a neutral vacancy are considered. Vacancy states are found to exist in the Si thermal gap for each structure. The character of these states is predominantly dangling-bond p-like localized on the four atoms surrounding the vacancy. The ideal (unreconstructed) vacancy yields an electronic spectrum, which is unstable with respect to Jahn-Teller type distortions. The two different reconstruction models considered yield Jahn-Teller stable situations.