Polarization effect of Schottky-barrier CdTe semiconductor detectors after electron irradiation

Spectrometric properties of cadmium telluride (CdTe) radiation semiconductor detectors with Schottky-barrier contacts were studied after irradiation with a high energy electron beam of 5 MeV-energy. The total cumulative dose of 2.25 kGy was delivered stepwise and the response of detectors to 241Am radioisotope source was acquired using a standard spectrometric chain at reverse bias voltages of 300 V, 400 V and 500 V. To evaluate the radiation damage, the spectral parameters of the 59.5 keV-photopeak were determined, namely the peak position, the full width at half maximum (FWHM), the peak amplitude and the net peak area. The time evolution of these parameters was followed by recording the spectra in 30-seconds (or 2-minutes) intervals after applying the reverse bias voltages. The results demonstrated significant effect of high energy electrons on the spectral characteristics even after applying the lowest dose of 0.5 kGy. The shift of the photopeak to lower energies, the increase of the FWHM and decrease of the peak height and area were confirmed. The time evolution of the observed tendencies disclosed that electron irradiation results in earlier onset of the polarization mechanism. After irradiating with the highest dose of 2.25 kGy, the polarization effect occurs practically immediately after applying the bias voltage.