Study of recombination processes in a-Si:H by the temperature dependence of the two carriers phototransport properties

We have studied films of undoped hydrogenated amorphous silicon by measuring their phototransport properties as a function of temperature. The samples were prepared by decomposition of silane using either the rf glow discharge or the hot-wire techniques. Both materials exhibit similar temperature dependences of the phototransport properties. The main difference is that the thermal quenching effects in the hot-wire material occur at a lower temperature. The results are consistent with the 'standard' recombination model, to which recombination through the bandtails is added. The differences in the thermal quenching effects are attributed to the higher density of conduction bandtail states in the hot-wire material, and to differences in the position of the Fermi level with respect to the dangling bond states.