Two-step passivation by K2S2O8 and NH4F/H2O2 solutions for improving the performance of CdZnTe detectors

Passivation plays a crucial role in surface treatment, which could generate an oxide layer that significantly decreases the surface leakage current of Cadmium zinc telluride (CdZnTe, CZT) detectors and enhancing their final performance. However, existing passivation methods are limited by the unevenness of the oxide layer and insufficient reduction in surface leakage current. In this paper, a novel two-step passivation method for CdZnTe is proposed, in which the first step uses potassium persulfate (K2S2O8) solution and followed by treatment with ammonium fluoride mixed with hydrogen peroxide (NH4F/H2O2) solution. The results indicate that the passivation method can produce a uniform oxide layer, and the surface leakage current was decreased by 77.76 %. In particular, the energy resolution was improved by 80 % after passivation. This is attributed to the fact that the two-step passivation method removes the highly conductive Te-rich layer, leaving only the tellurium oxide on the CdZnTe surface. Therefore, the two-step passivation method provides an effective passivation treatment process for preparing high-performance CdZnTe room-temperature radiation detector.