Microscopic structure of oxygen defects in gallium arsenide

Accurate total-energy pseudopotential methods an used to study the structur es, binding energies, and local vibrational modes of various models for the Ga-O-Ga defect in GaAs. We find that the previously proposed models, O-As (an off-centered substitutional oxygen in arsenic vacancy) and O-.(1) (an o xygen atom occupying a tetrahedral interstitial site), are inconsistent wit h experimental data. We introduce a model, (As-Ga)(2)-O-As (two arsenic ant isites and one off-centered substitutional oxygen in arsenic vacancy), the properties of which are in excellent agreement with experimental characteri zations. [S0163-1829(99)51648-2].