The paper is focused on the simulation, fabrication and measurement of the high UV detection performances of 6H-SiC pn photodiodes based on an efficient planar termination. The oxide ramp technology used for these photo-detectors is extensively presented. The OBIC technique was used for optical measurements of the samples. The impact of diode's bias as well as their photo-response on some incident light power values have been revealed by measurements and numerical simulations. The measurement shows a stronger bias effect on the diode optical properties than the simulation data.