Influence of Laser Radiation on Electrical Properties of CdZnTe Crystal

Cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) compound semiconductor crystal has been shown to be the most promising materials for X-ray and gamma ray detectors [1, 2]. It is due to possibility to use this material at room temperature. However, the yield of high- quality crystals is still limited due to presence of Te inclusions, crystal twins, dislocations, grain boundaries and other defects. Several researchers have shown a possibility to improve crystal quality by CO2 laser irradiation [3, 4]. The disadvantages of this method are long processing time - about 100 h and damage of crystal the surface. We have studied the influence of weakly absorbed laser radiation on CdZnTe crystal electrical properties and radiation detector parameters. CdZnTe crystal was grown by vertical gradient freezing method using high-purity Cd, Zn and Te. Grown crystal had high concentration of non-controllable impurities and Te inclusion. Infrared microscopy was used to characterize concentration of Te inclusions. CdZnTe samples where irradiated by Nd:YAG laser and afterwards current voltage (I-V) characteristic measurements were performed. I-V characteristic showed that the sample resistivity increased after irradiation by 700 laser pulses at intensity 6.6 MW/cm2. Treatment by higher intensity laser radiation leads to damage of the opposite side of the crystal. This effect is more pronounced with higher Te inclusion concentration. Moreover, scanning electron microscopy did not show any changes of chemical composition. CdZnTe samples performed as a better radiation detector after laser treatment due to reduction of leakage current by 30% and improved spectral energy resolution, especially at low quantum energies. References 1. T. E. Schlesinger, J. E. Toney, H. Yoon, YE. Lee, B. A. Brunett, L. Franks, R. B. James, Mat. sci. eng. R, 32, 103 (2001) 2. F. Lebrun. Nucl. instrum. meth., A. 563, 200 (2006