Tight-binding calculations on the electronic structure of neutral divacancies in the Ga-related III-V compound semiconductors

Abstract

We present a tight-binding theory for the calculations of the electronic structure of divacancies in compound semiconductors. The theory has taken both intra- and interatomic electron–electron interactions into account. The effect of charge transfer between the components of the complex defects on the electronic structure can thus be included in the calculations. We apply the theory to the electronic-structure calculations for the neutral divacancies in the Ga-related III-V compound semiconductors, GaP, GaAs, and GaSb. The calculations are done with the use of the recursion method and the supercell approximation. The energy positions and localizations of the deep levels for the defects are predicted. It is shown that each divacancy introduces seven defect levels, three at the edges of the lower gap and four in or around the fundamental band gap. A model for the description of the physical origin of these four fundamental gap-related defect levels is presented. It is also shown that for the neutral divacancy in the three Ga-related III-V compound semiconductors the last occupied a1 and e fundamental gap levels stay at very close energies and have very different localization characters.