Properties of hydrogenated amorphous silicon carbide films prepared by a separately excited plasma CVD method

In order to prepare high-quality hydrogenated amorphous silicon carbide ( ) films with a wide band gap, we propose use of a separately excited plasma CVD (SEPCVD) system composed of two independent plasma chambers and one deposition chamber. This method enables control of methane and silane plasmas independently. The optical and electrical properties and structure of films prepared by the SEPCVD method were evaluated with visible - ultraviolet absorption spectroscopy, infrared transmission spectroscopy, x-ray photoelectron spectroscopy and measurements of the photo- and dark conductivities. The carbon content and the optical band gap increased with increasing the rf power on both the methane side and the silane side. films with a carbon content above 0.6 and an optical band gap above 2.8 eV could be prepared by the SEPCVD method even though hydrogen-diluted gas was used. The SEPCVD method proved useful in preparing films with a wide gap. Both fourfold-coordinated carbon atoms and threefold-coordinated carbon atoms existed in films with carbon content from 0.5 to 0.6. However, the atomic percentage of threefold-coordinated carbon in films prepared by the SEPCVD method is smaller than that obtained by the conventional method. was 0.1 - 0.3 and increased with increasing rf power. and decreased with increasing rf power on the methane side, but they were not dependent on the rf power on the silane side. For films with an optical band gap between 1.8 eV and 2.0 eV, the photoconductivity and the photosensitivity were and respectively, and films with high photoconductivity could be prepared. However, the photoconductivity of the films with an optical band gap above 2.2 eV was about .