Local vibrational modes of Zn–H–As defects in GaAs, ZnSe and ZnTe

The hydrogenation of the zinc acceptor in GaAs (ZnGa), and As acceptor in ZnSe (AsSe) and in ZnTe (AsTe), is studied by computer modeling using an ab initio pseudopotential density-functional method. We found that the lowest energy location for hydrogen is nearly bond-centered (closer to As) between Zn and As atoms. Also for GaAs:ZnH, ZnSe:AsH and ZnTe:AsH, antibonding As–H units were found to be metastable by 0.4, 0.5 and 0.7 eV, respectively. The calculated local vibrational modes and deuterium isotopic shifts agree within less than 4% of the experimental data. The correct ordering of the As–H stretch modes in GaAs and ZnSe is only reproduced when anharmonic effects are taken into account.