Transport Properties of Intrinsic Hydrogenated Amorphous Silicon Produced by the Hot-Wire Technique Investigated by the Photomixing Technique

The transport properties of hydrogenated amorphous silicon (a-Si:H) with a hydrogen content ranging from 12% to less than 1%, which were produced by the hot-wire technique, varying the deposition substrate temperature, 290°C<T_S<400°C, were systematically studied by the photoconductive frequency mixing technique. With an increase of the deposition substrate temperature, and consequent decrease of hydrogen content, the photoconductivity, σ_pc, and the drift mobility, μ_d, are found to decrease, while the width of the conduction band tail, ε, increases. Continuous degradations of photoconductivity, drift mobility, and photomixing lifetime, τ, were found during light soaking experiments. In addition, it was found that the drift mobility increases and the photomixing lifetime decreases with an increase of the applied electric field, while the photoconductivity is essentially independent of the electric field within the range of 1000-10 000 V cm^-1. Furthermore, the electric field dependence of the drift mobility in the annealed state is always larger than in the light-soaked state. The results for the electric field dependence are explained using the model of long-range potential fluctuations, whose range can be determined by employing an analysis previously developed.