HYDROGEN DEFECT STATES IN GALLIUM-ARSENIDE - AB-INITIO CALCULATIONS

Ab initio calculations have been performed for the various hydrogen (o r muonium) charge states in GaAs. The equilibrium geometry of H+, H-0, and H- states and relative energies for trigonally symmetric sites on [111] axis were determined within two configurations of Ga7As7, clust ers. Effective core potentials were used on the Ga and As host atoms a nd all exterior bonds were terminated with hydrogens. The present resu lts are compared to available experimental information with emphasis o n recent Mu(-) data, and to previous theoretical treatments. We obtain a highly stable H- confined within a tetrahedral interstitial region with Ga nearest neighbours consistent with experimental findings.