Binding and formation energies of native defect pairs in GaAs.

The formation energies of native lattice-site point defects and of nearest neighbor lattice-site defect pairs in GaAs have been calculated using the self-consistent Greens function technique. From these results, we deduce a binding energy of ~2 eV +- 1 eV for the pairs V(As)+V(Ga,)As(Ga) +Ga(As,)As (Ga) +V(As,) and Ga(As) +V(Ga). We also obtain endpoint energy differences for the vacancy migration hope V(Ga -> V(As) +As (Ga) and V (As) -> V(Ga) +Ga(As). For these latter reactions, violent donor-acceptor transitions occur and the Fermi energy determines the stable form.