The stability of mono-atomic H in crystals was studied by using the quantum-chemical intermediate neglect of differential overlap method. Various interstitial positions were considered for H, and their energetic preferences were studied for intrinsic, n-type and p-type samples. It was noted that the 1-electron energy level was situated at about 1.4eV below the bottom of the valence band, and was composed mainly of H 1s and As (closest to H atom) 4s states in the case of a H atom which was placed in a BC site. The simulations also showed that, in the case of the Td(a) position for n-type GaAs, the defect level was located at 0.4eV above the top of the valence band. This was composed mainly of the H 1s orbital but, in other cases, the H 1s wave-function seemed to be rather extended.

A.Stashans, M.Kitamura: Solid State Communications, 1996, 99[8], 583-8