SiO 2 layers were deposited onto SiC by photo-chemical vapor deposition (photo-CVD) using deuterium (D 2 ) lamp as the excitation source. For the photo-SiO 2 deposited 500 o C, interface state density (D i t ) was estimated to be 5.66x10 1 1 cm - 2 eV - 1 . With an applied electric field of 4 MV cm - 1 , it was found that the leakage current was only 3.15x10 - 8 A cm - 2 for the photo-CVD SiO 2 layer prepared at 500 o C. It was also found that photo-SiO 2 could effectively suppress dark current of SiC-based photodetectors (PDs). It was found that we could reduce dark current of SiC-based PDs by about three orders of magnitude by the insertion of a 5 nm-thick photo-CVD SiO 2 film in between Indium-tin-oxide (ITO) contact and the underneath SiC. Photocurrent to dark current ratio of ITO/SiO 2 /SiC MIS PDs was also found to be much larger than that of conventional ITO/SiC Schottky barrier PDs.