Electronic structure and binding energy of theAsGa-Asipair in GaAs: EL2 and the mobility of interstitial arsenic

Abstract

The binding energy and electronic structure of the ${\mathrm{As}}_{\mathrm{Ga}}$-${\mathrm{As}}_{\mathrm{i}}$ defect pair in GaAs has been calculated using the self-consistent Green’s-function technique. The arsenic interstitial ion was placed along a [111] antibonding direction relative to the arsenic antisite ion. At a separation of one bond length, we find that ${\mathrm{As}}_{\mathrm{i}}$ is bound in n-type material and unbound in p-type. The relative stability of the interstitial defect in the two $T_d$ sites (at a distance of one and two bond lengths from ${\mathrm{As}}_{\mathrm{Ga})}$ also depends on the Fermi energy. These calculations raise questions about, and propose a definitive test for, a recent microscopic model of the structure of EL2.