Surface sink effect driven defect evolution and performance degradation mechanism in proton irradiated CdZnTe detectors

Cadmium Zinc Telluride (CdZnTe) has become a key semiconductor material for room-temperature γ-ray detectors. However, its performance and service life can be severely compromised by radiation damage in harsh radiation environments, particularly in space where protons constitute the predominant high-energy particles. In this work, we reveal an anomalous reduction in surface roughness of the CdZnTe crystals after proton irradiation, which is attributed to the predominance of smoothing mechanisms, such as the Herring-Mullins diffusion mechanism and radiation-induced viscous flow. Transmission electron microscopy (TEM) analysis elucidates the depth-dependent defect distribution in irradiated CdZnTe crystals. Frank loops and defect clusters dominate in the near-surface region, while stacking faults dominate in deeper regions, primarily due to the surface sink effect. Current-mode deep level transient spectroscopy (I-DLTS) analysis reveals a significant increase in defect concentration and the emergence of deep traps at higher fluences, leading to a sharp rise in the ratio of carrier detrapping time to capture time. These microstructural changes directly lead to the degradation of electrical and detection performances. Electron mobility decreases from 1087 cm²V^-1s^-1 before irradiation to 412 cm²V^-1s^-1 after irradiation. CdZnTe detector completely fails at the fluence of 5 × 10¹¹ p/cm². We systematically investigated the underlying mechanism of irradiation defect-induced performance degradation in CdZnTe crystals after proton irradiation, providing innovative design strategies and theoretical tools for accurately evaluating and enhancing the radiation tolerance and service reliability of CdZnTe detectors in space environments.