This thesis describes the deposition characteristics and physical properties of hydrogenated amorphous silicon carbide (a-SiC:H) films prepared by Plasma Enhanced Chemical Vapor Deposition. In order to examine the effect of hydrocarbon gases on the structural and optoelectronic properties of a-SiC:H films, a-SiC:H films have been prepared from gas mixtures of $C_3H_8-SiH_4-H_2,\; CH_4-SiH_4-H_2\;\;\mbox{and}\;\; CH_4-SiH_4-H_2$. These films were characterized by infrared absorption, optical absorption, Raman and X-ray photoelectron spectroscopy. At the same carbon concentration in the gas mixtures, propane allows more carbon and hydrogen atoms to be effectively incorporated into the film than does methane. IR spectra reveal that the structure of propane-based films has the characteristics of that of two kinds of films, methane- and ethylene-based films. It is found that the type of hydrocarbon gas strongly affects the bonding structure and the composition of the films. From these results, it is proposed that the use of propane is suitable for the fabrication of high-quality a-SiC:H with a wide optical bandgap ($>2.0 eV$) and a deposition rate of $\sim 2$ A/s. To study the influence of hydrogen on the structural and optoelectronic properties of the propane-based films, the properties of the films deposited at different substrate temperatures ($T_s$) are systematically investigated using infrared and ultraviolet-visible (UV) absorption spectroscopies. By observing the change of intensities of IR absorption peaks could be assigned more accurately. When $T_s$ is increased up to $300\,^\circ\!C$, intensities of $CH_3$ and $SiH_2$ groups are reduced, indicating the formation of a dense network structure. From these results, the degradation of electrical properties in a-SiC:H films is attributed to the formation of undesirable microstructure, such as microvoids and polyhydride bondings, which is related to the incorporation of carbon in the form of $CH_3$ group into the films. By varying the flow rate of $H_2$ in the mixture, a systematic study has been carried out on the influence of $H_2$ dilution on the structural and properties of three types of a-SiC:H films. a-SiC:H films have been prepared from gas mixture of $C_2H_2-SiH_4,\; C_3H_8-SiH_4\;\; \mbox{and}\;\; CH_4-SiH_4$, diluted with $H_2$. These films were characterized by infrared absorption, optical absorption, electron spin resonance, Raman and Auger electron spectroscopy. The structure of a-SiC:H films are also analyzed by hydrogen evolution experiments using a modified gas chromatography. $H_2$ dilution affects the structure and composition of the films, which is closely related to the reactivity of hydrocarbon gas. Under high $T_2$ condition, $H_2$ dilution to $C_2H_2-SiH_4$ mixture results in a decrease of the amount of undesirable microstructure and carbon in the films, indicating the formation of a dense network structure. It is suggested that $H_2$ dilution produces a dense network structure by increasing the surface mobility of the adsorbed radicals during the film growth. By diluting $C_2H_2-SiH_4$ mixture with $H_2$, it is possible to prepare high-quality of a-SiC:H films with high deposition rate.
