Divacancies in the Ga-related III-V compound semiconductors: Electronic structure and charge states.

Abstract

We report on theoretical calculations for the electronic structure of the divacancies at different charge states in the three Ga-related III-V compound semiconductors, GaP, GaAs, and GaSb, based on a self-consistent tight-binding theory. The calculations are done with the use of the recursion method and the supercell approximation. We show that the divacancies can have many charge states. We calculate the energy positions and localizations of the defect levels for the predicted charge states. We find that each divacancy at a charge state introduces seven defect levels, three at the edges of the lower gap and four in or around the fundamental band gap. We present a molecular-orbital treatment of the four fundamental gap-related defect levels. We also find that the two defect levels in the lower half of the fundamental band gap stay at close energies and have an energy ordering that is dependent on the charge state of the defect. We critically compare the results of our calculations with experiments and other theoretical calculations. We argue that in the calculations for the divacancies in the III-V compound semiconductors, it is important to eliminate the self-interactions from the self-consistent defect potentials.