Spectroscopic Studies of Ni/CdTe/Au Schottky Diode X/γ-ray Detectors

Abstract

This research is devoted to spectroscopic studies of Ni/CdTe/Au diode detectors with a high barrier Schottky contact at the Ni-CdTe interface and near Ohmic contact at the Au-CdTe interface. Both contacts were formed on the opposite sides of high resistivity CdTe(111) crystals after preliminary chemical and ion etchings. The detectors had low dark current (2-3 nA at 1000 V) and were tested using ¹³⁷Cs, ⁵⁷Co and ²⁴¹ Am isotopes as radiation sources. Quite high energy resolution (0.9%@662keV at 800 V) was obtained in the ¹³⁷Cs spectrum at room temperature. In the spectra of ⁵⁷Co and ²⁴¹Am isotopes an increase in bias voltage resulted in competing processes: efficient collection of photogenerated charge carriers and harmful increase in reverse current. There were optimal values of bias voltages to achieve sufficient detection efficiency and energy resolution of every detector for radiation of different isotopes. The most interesting and important feature of the developed Ni/CdTe/Au Schottky diode detectors was the absence of degradation of the parameters with time. Moreover, the optimization of the spectroscopic characteristics (FWHM, peak counts, peak to valley ratio, peak channel position, etc.) of the Ni/CdTe/Au diode biased and subjected to irradiation from a ¹³⁷Cs isotope was observed under long time detector operation.