Metastable State ofEL2in GaAs

The metastable state of the $\mathrm{EL}2\mathrm{}$ defect in GaAs is characterized by the absence of any experimentally observed defect level. We present a model of its atomic configuration, which allows a simple interpretation of this nonobservation as well as the direct and reverse transitions from the stable to this metastable state. The model consists of a split interstitial configuration of the initial stable ${\mathrm{As}}_{\mathrm{Ga}}-{\mathrm{As}}_i$ pair. We first use simple physical arguments to show that this configuration has the required electronic properties. We then substantiate these arguments by a full calculation of the local atomic configuration and of the corresponding electronic structure.