Effect of cobalt 60 and 1 MeV electron irradiation on silicon photodiodes/solar cells

Abstract

Using 10–60 krad doses of cobalt 60 gamma radiation, the effect of simulated space radiation on 1 mm2 active area silicon photodiodes with a sapphire window is studied. The diodes will be used to control the laser output of a space experiment in geostationary orbit. The effect of 1 MeV electron irradiation with various fluences on 100 mm2 silicon photodiodes/solar cells, which were used to control the attitude of a satellite in space, is also studied here. Fluences ranging from 3 x 1014 to 1 x 1015 cm–2 of 1 MeV energy, caused a decrease in the short-circuit current, i.e., increasing the percentage of deterioration from 12% to 20% at a room-temperature measurement. Exposure to the gamma irradiation yields almost no degradation for the electro-optical performance of the devices. The manufacturing processes of the detectors and their electro-optical I–V characteristics such as fill factor, responsivity, and dark current are presented here. Electro-optical tests were also done at intermediate levels of irradiation. High stability and high quality of the photodiodes were achieved prior to and after irradiation. PACS No.: 84.60J