Tight-binding calculation of orbital relaxations and hopping integral modifications around vacancies and antisite defects in GaAs

Abstract

We study the influence of changes in the tight-binding parameters around point defects in semiconductors and we apply our method to study the various charge states of the vacancies and anti-site defects in GaAs. We take into account the changes in the hopping integrals between two nearest neighbours of a vacancy which arise from the lifting of the orthogonality condition between the orbitals of the removed atom and the orbitals of the neighbouring atoms. We take into account the changes in the hopping integrals between a substitutional defect and its nearest neighbours which arise from the differences between the orbitals of the substitutional defect and the orbitals of the substituted atom. Lastly, we take into account the changes in the energy levels of the nearest neighbours of a defect which arise from the electronic rearrangement around the defect. We propose a systematic method to calculate these changes and we investigate their consequences on the electronic structure of the various charge states of the vacancies and anti-site defects in GaAs. We compare our results with other tight-binding calculations where these changes have not been taken into account Etude de l'effet des modifications des parametres de liaisons fortes autour de defauts ponctuels dans les semiconducteurs sur leur structure electronique. Application a l'etude des divers etats de charge des lacunes et des defauts antisite dans GaAs