Quantitative Analysis of Energy Spectrum Distortion for CdZnTe Detector

Cadmium Zinc Telluride (CZT) has combined relatively high atomic number (Cd48, Zn30, and Te52) with enough bandgap energy (1.52 eV) to permit room temperature operation. Hence, a semiconductor detector made of CZT has been employed in scientific and technological fields, most notably in medical imaging and high energy astrophysics. However, due to the low transport properties of carriers, electron-hole pairs generated in CZT sensor by irradiated radiations cannot be completely collected. Eventually, this problem leads to a significant distortion of the spectrum. The distortion of radiation energy spectrum could be described with a model of charge drift in the semiconductor material and charge induction on the electrodes (cathode and anode). Therefore, the analysis of the suitable model for ion-pair (electron and hole) drift is very important thing to simulate the radiation response of CZT detector. In this study, the simple model dependent on the interaction positions of incident radiations and mobility lifetime (μ τ) of ion-pairs was studied to predict the charge collection efficiency on electrodes. Evident difference of energy spectrum caused by reflecting charge collection efficiency was evaluated for a CZT detector (5x5x5 mm3) widely used in spectroscopy, using the Monte Carlo codes