EFFECT OF HIGH-ENERGY PROTONS ON 4H-SiC RADIATION DETECTORS

We present investigation of high energy radiation detectors based on 4H-SiC as influenced by irradiation with 24 GeV proton doses of up to 10 cm. SiC detectors have been produced from n-type 4H-SiC epilayers grown on the top of the n-type substrate. They were supplied with a nickel ohmic contact on the back surface and a gold Schottky contact on the top. Activities and numbers of Be and Na atoms produced in SiC detectors after the irradiation were measured experimentally. Activities of other radionuclides were calculated on the basis of this data. Activities of Be and Na were proportional to the total irradiation dose and ranged from 1.3 to 890 Bq and from 1.9 to 950 Bq, respectively. In the samples irradiated with 1 · 10 and 1 · 10 protons/cm 390 days after the irradiation the number of radiated electrons with different energies was from 1.0 to 600 per second, respectively. Contact properties of the devices were investigated by means of the current–voltage (I–V ) characteristics. It was found that proton irradiation with the highest doses leads to the significant changes of the contact properties. Namely, the contact potential barrier grows from about 0.7–0.75 eV in the pristine and less irradiated samples up to about 0.84 eV in the detectors irradiated by highest doses. Moreover, rectifying behaviour of the Schottky contacts becomes much less expressed upon irradiation, tending to become nearly symmetrical. The observed behaviour probably can be explained by the appearance of the irradiation-induced inhomogeneous regions of detectors that limits the applicability of classical contact theory.