New insight into the 1.1-eV trap level in CdTe-based semiconductor

We investigated trap levels in detector-grade CdZnTe (CZT) material grown by using three different methods, viz, the Bridgman, traveling heater method (THM), and high-pressure Bridgman method (HPB), by current deep-level transient spectroscopy (I-DLTS). All CZT detectors contained deep trap levels located at around 1.1 eV (which we designated DE1), which has been attributed to Te vacancies induced one. However, our crystal growth and characterization results indicated that dislocations induced by Te secondary defects (inclusions/precipitates)were a more probable origin than Te vacancies. Also, a theoretical calculation of the electron de-trapping time associated with DE1 can explain well the abnormal residual current behavior at temperatures slightly above room temperature. Our results show better control of the concentrations and the sizes of Te secondary defects is critical to improving the detector's performance at room temperature by reducing lagging effects.