Electronic structure of the isolated vacancies and divacancy in InP

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Abstract
Within the self-consistent semiempirical tight-binding theory, a study of the electronic structure of the undistorted vacancies and divacancy in InP has been performed using the Lanczos-Haydock recursion method. We predict the energy positions and the localizations of the deep levels for all possible charge states of these vacancy defects. In the cases of the isolated In and P vacancies, we find that with the Fermi level at energies above the midpoint of the fundamental band gap, the two isolated vacancies stay at opposite charge states and thus attract each other. In the case of the divacancy, we demonstrate that the defect can have many different charge states, and introduces many deep levels at energies around the middle of the fundamental band gap, revealing the complex nature of the defect. A model for the description of the electronic structure of the divacancy is presented. We discuss the complicated structure of the deep levels of the divacancy in all its charge states in terms of the calculated localizations of these levels. We compare our calculated results for the isolated In and P vacancies with local-density calculations. We show also that in the calculation for the divacancy, it is important for the self-interaction to be well accounted for.