A CdZnTe (CZT) detector is a compound semiconductor detector with a high atomic number and high detection efficiency, it can be used at room temperatures to detect short wavelength radiation such as X-ray and γ ray.

This study aims to investigate the factors affecting the energy spectrum characteristics of the CZT detector.

The geometric model of the detector was established by using Geant4 software, and the intrinsic detection efficiency and absorption rate of CZT crystal in the planar size of 10 cm×10 cm were simulated. The charge collection efficiency of the crystal was calculated using the Hecht formula and the γ-ray energy spectrum was obtained by collecting the deposition energy and position information in the crystal. By analyzing the physical properties of crystals, the impact of physical properties on detector performance was explored.

Simulation results show that incomplete charge collection significantly influences the spectral performance of the detector. When the γ ray energy is less than 50 keV, the spectrum is not affected by hole wake whilst the influence of hole wake is more obvious when the energy is between 50 keV and 100 keV. The energy spectrum is gradually aggravated by the influence of hole wake when the γ ray energy is above 100 keV.

This effect of hole wake for CZT detector can be reduced by increasing the bias voltage, but the increased bias voltage shifts the spectrum's peak, and the shift amount is determined by the maximum charge collection efficiency of the crystal.