Wide band gap a-SiOx:H films have been prepared by the photochemical decomposition of a SiH4, CO2 and H-2 gas mixture. Deposition parameters namely the CO2 to SiH4 gas flow ratio, HP dilution and chamber pressure were optimized in order to achieve highly photoconducting (1x10(-6) S cm(-1)) films with an optical gap of 1.99 eV. The optical gap was found to increase with an increase in the CO2 to SiH4 flow ratio. A decrease in the photoconductivity, refractive index, spin g-value and a simultaneous increase in the spin density are attributed to an incorporation of oxygen into the films. Upon hydrogen dilution the photoconductivity of a-SiOx : H films was observed to improve along with an increase of the optical gap. The spin density of a-SiOx : if films was of the order of 10(17) cm(-9). The optoelectronic properties of the films have been correlated with the bonding configurations in the film, deposition parameters and the growth kinetics.