Improved transport properties of microcrystalline silicon films grown by HWCVD with a variable hydrogen dilution process

The structure and the transport properties of microcrystalline silicon films prepared by hot-wire/catalytic chemical vapor deposition (HWCVD/Cat-CVD), using different dilution ratios of silane in hydrogen, were investigated. Spectroscopic ellipsometry analysis revealed an increase in the thickness of amorphous incubation layer formed before nucleation and a reduction of the void volume fraction when hydrogen dilution decreases. Thus, a specific microcrystalline silicon film growth process was proposed, based on a variable dilution of silane in hydrogen. For films prepared in such conditions, the formation of the incubation layer was inhibited, which led to a drastic improvement in carrier transport along the growth direction as proved by the diffusion-induced time-resolved microwave conductivity data.