The Effect of Indium Doping on Deep Level Defects and Electrical Properties of CdZnTe

CdZnTe (CZT) ingots doped with different concentrations of indium (2 ppm, 5 ppm, 8 ppm, and 11 ppm) were grown by the Vertical Bridgman Method. The charge transport behaviors of CZT wafers were characterized by Thermally Stimulated Current (TSC), Time of Flight technique (TOF) and Current-Voltage measurements (I-V). TSC results indicate that the concentration of deep donor defects TeCd2+ is reduced significantly by increasing indium dopant content from 2 ppm to 8 ppm, while that of indium related traps, InCd+and A-centers, is sharply increased. Hecht fitting and TOF results indicate that the electron mobility keeps nearly unchanged for different dopant concentrations in the region between 2 ppm and 5 ppm, but the lifetime increased greatly with increasing indium dopant concentration. Therefore, (mu tau)(e) value was increased with higher indium dopant. The up-shift of Fermi level is also observed in the temperature-dependent I-V result with the increasing of indium dopant content. Large Schottky barriers are found in detectors with higher indium concentration. High voltage x-ray response results show that the channel number shifts to the low energy side for 2 ppm dopant samples compared with best performance 5 ppm dopant samples, while the full-energy peaks are broadened for 8 ppm and 11 ppm dopant samples.