The properties of bismuth-doped vacuum-evaporated CdS films

The effect of doping with bismuth on various properties of vacuum-evaporated CdS films was studied. The properties specifically studied were (1) the dark conductivity and photoconductivity as functions of the temperature and doping concentration, (2) the Hall mobility and carrier concentration at room temperature, (3) the thermally stimulated current and (4) the optical absorption and spectral response. It was found that on doping with bismuth the dark conductivity decreases and the photosensitivity increases significantly. These phenomena probably arise from the formation of cadmium vacancies due to bismuth doping. Studies of the Hall effect show that the carrier concentration is reduced by doping with bismuth. Investigations of thermally stimulated currents for both pure and doped films show that the trap concentrations are reduced by doping.