Anion-antisite-like defects in III-V compounds

We report ab initio calculations of total energies and electronic structures of P, As, and Sb donors in GaAs and InP. In the ${\mathit{T}}_{\mathit{d}}$ geometry, all these defects exhibit two donor states in the forbidden gap: an internal optical excitation energy of the order of 1 eV, and a Franck-Condon shift of the order of 0.1 eV. All these defects possess a metastable geometry of the electrically neutral vacancy-interstitial pair with no donor states in the band gap. We discuss the differences between the six systems and explain why an optically inducible transition to the metastable state is inefficient for GaAs:${\mathrm{Sb}}_{\mathrm{Ga}}$.