Hydrogenated amorphous silicon carbide alloys are being investigated as a possible top photoelectrode in photoelectrochemical cells used for hydrogen production through water splitting. In order to be used as such, it is important that the effects of carbon concentration on bonding, and thus on the electronic and optical properties, is well understood. Electron spin resonance experiments were performed under varying experimental conditions to study the defect concentrations. The dominant defects are silicon dangling bonds. At room temperature, the spin densities varied between 1016 and 1018 spins/cm3 depending on the carbon concentration. Photothermal deflection spectroscopy, which is an extremely sensitive measurement of low levels of absorption in thin films, was performed to investigate the slope of the Urbach tail. These slopes are 78 meV for films containing the lowest carbon concentration and 98 meV for those containing the highest carbon concentration.