Hydrogen-induced states near the GaAs band edges

In the present study the link between the inclusion of H species in GaAs and the appearance in the band gap of near-band-edge energy levels has been investigated. The equilibrium geometries and the electronic structures relative to different locations of H atoms, ions, and dimers in the GaAs lattice have been evaluated by first-principle local-density-functional methods. Atomic arrangements in GaAs identical to those found for different equilibrium geometries of the H species, but with the H species removed, have also been investigated in order to separate the effects of the lattice deformations due to the H inclusion from those produced by the formation of H-host-atom bonds. Discrete near-edge levels appear in the band gap, which are induced by the H interactions with the GaAs lattice as well as by charge effects in the case of H ions. Finally, radiative transitions from the conduction-band to the valence-band near-edge states are shown to account for the main features of the emission bands observed in the photoluminescence spectra of hydrogenated III-V compounds.