Isolated arsenic-antisite defect in GaAs and the properties ofEL2

We report parameter-free, self-consistent calculations of the electronic structures, total energies, and forces of the ${\mathrm{As}}_{\mathrm{Ga}}$ antisite, of an As-interstitial–Ga-vacancy defect pair, and of various configurations between these limits. The corresponding total-energy surface exhibits an interesting metastability. The results are discussed with respect to photoquenching, thermal stability, optical, electronic, and magnetic properties of EL2. This comparison shows that the behavior of EL2 may be understood in terms of the isolated arsenic antisite, which exhibits via the mentioned metastability (${\mathrm{As}}_{\mathrm{Ga}\mathrm{?}}$ ${\mathrm{As}}_{\mathrm{i}}$) and the dissociation and/or association (As?${\mathrm{VGaAs}}_{\mathrm{i}}$) a variety of different properties. It is pointed out that this new mechanism of metastability may be significant for other point defects in semiconductors as well.