Amorphous silicon oxy-nitride (a-SixOyN1-x-y) films with refractive indices in a wide range of 1.43-1.75 were obtained by plasma-enhanced chemical vapour deposition of silane, nitrous oxide, and ammonia gases at 30°C. Photonic crystal slabs based on a-SixOyN1-x-y material systems were simulated and fabricated. Low-contrast photonic crystal structures for which the refractive index difference between the cladding and the core is small are implemented using this technology. It is shown that even low-contrast photonic crystals can provide fairly wide bandgap. The films were patterned by electron-beam lithography and etched by reactive ion etching. The device fabrication is carried out at low temperature and is independent of the substrate type. Therefore, this technology can be used to integrate photonic crystal-based optical integrated circuits within silicon- and GaAs-based integrated circuits.