Serious Degradation Characters of CdTe Nuclear Detector by Electron or Gamma Irradiations

We present the degradation characteristics of M-S-M (metal-semiconductor-metal) type CdTe nuclear detectors fabricated from undoped p-type THM crystals under successive irradiations of 60Co gamma rays and 2 MeV electrons at room temperature. Radiation-induced degradations on detector performances are investigated by the evaluations both of the photopeak and Compton edge of 241Am and 137Cs gamma rays. The FWHM energy resolution and counting rate of the photopeak become worse with increasing gamma ana electron fluences. It is thus concluded that the μτ product in the electrons and holes are decreased in comparison with that before irradiation, probably due to the carrier trapping effect. Comparing with the radiation effects of a Si surface-barrier detector, we discuss the annealing behavior of the irradiated CdTe detector.