Electronic transport in hydrogenated microcrystalline silicon: similarities with amorphous silicon

Undoped hydrogenated microcrystalline silicon (μc-Si:H) layers were grown by the very high frequency glow discharge (VHF-GD) technique under various deposition conditions. The electronic transport properties under illumination were investigated by means of steady-state photoconductivity and steady-state photocarrier grating methods. Similarly to hydrogenated amorphous silicon (a-Si:H), power law dependencies as a function of the generation rate are observed for the photoconductivity, for the ambipolar diffusion length, and for the parameter b (indicating the Fermi level). For μc-Si:H, as for a-Si:H, nearly constant product of (mobility × recombination time) of majority and minority carriers is observed as a function of the parameter b. Based on these similarities, we assume that the electronic transport model developed for a-Si:H remains valid for μc-Si:H.