We have prepared unhoped a-Si:H films by mercury-sensitized photo-CVD under various conditions. Electrical, optical, and structural properties were investigated. The deposition rate of 1.25 Å/sec has been obtained by optimizing the pressure of SiH4 + Hg in the reaction chamber and the distance between Hg lamp and substrate surface. The maximum ratio of the photoconductivity (100 mW./㎠) to the dark conductivity at 310 K was $6\times10^5$ with an optical gap of 1.81 eV for the sample of Tsub = 200℃. Also the minimum defect density of the film was obtained for the same sample. And the result of FTIR spectra indicated that the films prepared above 200℃ show sharper absorption tail than those below 200℃. We concluded that the samples prepared by photo-CVD are comparable to high quality samples prepared by GD (glow discharge).
