Energy Spectrum Correction and Carrier Mobility Calculation of CdZnTe Pixel Detector Based on the Depth of Interaction

An experimental method was described to calibrate the depth of interaction (DOI) of high-energy $\gamma $ -ray in large-size thick pixel CdZnTe detector. The experimental results indicated that the ratio of the cathode and anode amplitude strongly showed linear relationship with the DOI of incidence $\gamma $ -rays and the detector. The correlation coefficients were optimized. Based on the experimental calibration of DOI, the photoelectric effect signals from the depth range where the energy resolution and the photopeak location are high were screened out to draw the energy spectrum. In this way, the energy resolution of the CdZnTe pixel detector was improved to 0.707% for ¹³⁷ Cs@662 keV. Further combined with the anode rise time, the electron mobility of CdZnTe in 2-D (1 mm accuracy) and 3-D (2 mm $\times $ 2 mm $\times $ 1 mm accuracy) scales was calculated. At different pixel positions and depths in CdZnTe detector, the electron mobility varies between 1000 and 1150 cm ² /( $\text{V}\cdot \text{s}$ ).