Structural properties and energetics of oxygen impurities in GaAs

摘要: We investigate the structural properties, formation energies, and electronic structure of oxygen impurities in GaAs using first-principles total-energy calculations. Five charge states occupying an arsenic site (OAs) various interstitial sites (O i) were considered. For OAs defect negative we find off-center configurations withC2v symmetry as reported experimentally. Our results for energies reveal a negative-U behavior defect, which paramagnetic 22 is never stable. Oi three equilibrium O atom, are present all investigated. The stable configuration neutral shows atom between As-Ga pair forming As-O-Ga structure. However, states, exactly at tetrahedral site, bonding with four gallium first neighbors. Further, that 12 state stable, suggesting also exhibits negative- U behavior. Based on our results, suggest A, B8, B bands local-vibrational-mode absorption spectrum due to defect. Also show this cannot be associated interstitial-oxygen previously proposed.