Using first-principles calculations, the electronic structure of the P-vacancy pair in Si was studied. Detailed analysis of the atomic displacement fields associated with the atomic structure optimization after the defect formation indicated a strong dependence of the character and magnitude of relaxation both on the super-cell size and the E-center charge state. The simulation results strongly suggested that the E-center structure was of resonant-bond type, with a strong localization of an electron pair at the P atom. The energy level splitting for shared electrons in a vacancy due to the appearance of the resonance distortion was considered, as well as the nature of, and the reasons for, the level occupation.

Electronic Structure of the Phosphorus-Vacancy Complex in Silicon - a Resonant-Bond Model. M.G.Ganchenkova, A.Y.Kuznetsov, R.M.Nieminen: Physical Review B, 2004, 70[11], 115204 (11pp)