Bias-induced relaxation phenomena in current temporal behaviors of CdZnTe radiation detectors

The bias-induced temporal behavior of the dark current in CdZnTe radiation detectors essentially determines the detector's performance, but the traditional electric field dependent Schottky barrier height model cannot explain the complicated current transient behavior observed in experiments. In this work, dark current temporal response in CdZnTe detectors as a function of temperature is investigated both experimentally and numerically. After biasing, the transient current increases for detectors with small barrier heights, while decreases for those with large barrier heights before reaching the steady state. This current saturation process is attributed to the de-trapping of deep level defects. The evolution of the electric potential, electric field and trap occupancy in the detector is simulated, which shows an agreement with the measurement results. Schottky barrier height dependent electric potential distribution between bulk material and depletion layer at the blocking contact is responsible for different dark current temporal behavior in CdZnTe detectors.