The temperature dependences of steady-state photo-luminescence(PL) and photoconductivity($σ_ph$) in hydrogenated amorphous silicon(a-Si:H) have been investigated. A model for recombination processes in a-Si:H has been developed in order to explain the results of the experimental observations.
The existence of shallow radiative hole trap centers is assumed, and transitions between localized states are included in the model in addition to those between extended and localized states. The temperature dependence of the PL below 100K, which is quite different from that above 100K, is probably due to the power-law temperature dependence of the capture cross sections for these radiative hole trap centers. Temperature-dependent recombination kinetics in our model gives a good explanation of the experimental results for photoconductivity.
Finally, the nature of light-induced defects is discussed, and it is concluded that the main defect created by prolonged illumination is the silicon dangling bond.