Neutralisation of group vi donors by hydrogen in gallium arsenide

The infrared absorption of GaAs:S and GaAs:Te samples partially neutralised by hydrogen show two local modes with very similar frequencies. These modes are comparable to the ones already reported in GaAs:Se. These results are interpreted by assuming that neutralisation takes place by the formation of a bond between a Ga atom first neighbour of the chalcogen and a H atom in an antibonding location. This assumption is strengthened by ab initio calculations that provide also frequencies of the right order of magnitude.