Wide Optical-Gap a-Si:O:H Films Prepared from SiH4–CO2 Gas Mixture

Hydrogenated amorphous silicon oxygen alloy films (a-Si:O:H) with wide optical-gap have been prepared by rf glow discharge decomposition of CO2 and SiH4 gas mixture. The optical-gap increases monotonically from 1.76 eV to 2.43 eV with increasing molar fraction of CO2 to SiH4 in the gas phase. A high photoconductivity of 4.1×10-9(Ω·cm)-1 is obtained for the films with the optical-gap of 2.43 eV. Efficient doping is possible in these films and these properties suggest that the films are useful as window materials of photodetectors.