Gamma-Ray Spectroscopic Performance of Large-Area CdTe-Based Schottky Diodes

Spectroscopic performance of the Ni/CdTe/Au Schottky diode X/γ-ray detectors was examined by measurements of ¹³⁷Cs isotope spectra at different bias voltages and operation time. Both the Schottky (Ni-CdTe) and near Ohmic (Au-CdTe) contacts were formed on the opposite sides (10 × 10 mm²) of high resistivity CdTe(111) crystals after preliminary chemical etching and Ar-ion bombardment with different parameters. The detectors had low reverse dark current density (4–6 nA/cm² and 8–12 nA/cm² at bias of 500 V and 1000 V, respectively) and showed quite high energy resolution (2–4%@662 keV) at room temperature. The optimal bias voltage ranges for the Ni/CdTe/Au detectors were determined to achieve sufficiently high detection efficiency and energy resolution. These parameters were changing by 30–50% for the detectors biased and subjected to γ-ray radiation during several hours that evidenced quite low degradation. The detector spectroscopic parameters can be recovered by turning off the bias for seconds and turned on it again to continue measurements.