Radiation effects in ultraviolet sensitive SiC photodiodes

We tested SiC photodiodes with Co-60 gammas, 32 MeV protons and 14 MeV neutrons. The UV-photocurrent decreased to about 50% of its initial value at a total gamma dose of 40 kGy (Air). Nearly the same decrease was observed during proton irradiations of 9/spl times/10/sup 12/ cm/sup -2/. But after a neutron fluence of 1.5/spl times/10/sup 13/ cm/sup -2/ the signal was still 85% of that before irradiation. It is shown that the decrease of the photocurrent is caused by darkening of the glass window. Some of the color-centres could be annealed with the intense UV-light of a deuterium lamp. Furthermore hydrogen treatment of the photodiode reduces the radiation effects by about 20%.