Features of electrical and spectrometric properties of series connected CdTe-based Schottky-diode X/γ-ray detectors

The electrical and spectroscopic characteristics of the ionizing radiation detectors, designed as Ti/CdTe/Au diodes with a rectifying barrier were investigated. Schottky (Ti/CdTe) and ohmic (Au/CdTe) contacts were formed on the B- and A-faces of detector-grade p-CdTe(111) crystals subjected to Ar plasma treatment. Owing to the advantages of the fabrication technique, the Ti/CdTe/Au Schottky-diode X/gamma-ray detectors with similar parameters were obtained. The features of the single detector and stacks of two mounted detectors, connected in parallel or series, were analyzed. The measurements of the I-V characteristics showed that the sensor, consisting of two series-connected detectors, has lower dark current and significantly the weakened effect of space-charge-limited currents (SCLC) than the single detector or two parallel-connected detectors. The stack of the detectors connected in parallel has higher photosensitivity but lower energy resolution compared with those characteristics of the single detector. The analysis of the emission spectra of Cs-137 and Am-241 isotopes, measured at room temperature, showed that the sensitivity of the stack of the series-connected detectors turned out to be the highest. However, the double peaks were observed in the isotope spectra taken with such detector stack that was unusual and attributed to features of the electronic signal processing. Series connection of detectors has the advantages as reducing the dark current and decreasing the stack capacitance. To implement these features and optimally use such connection, specific electronic devices are needed, in particular to combine two charge packets which are formed by the detector stack into one with a larger amplitude.