Study Of The Defects And Annealing Of CZT Crytals

Cadmium Zinc Telluride(Cd_1-xZn_xTe or CZT) crystal is an room temperature nuclear radiation detector material with excellent properties. It can be used to fabricate X-ray and γ-ray detectors because of its high resistivity, low dark current, good thermal stability, wide and adjustable band gap, high energy resolution of the detecting ray, etc. In recent years, it has given rise to much attention and become hot pot of research in the world. However, some factors, including high growing temperature, low heat conductivity, high equilibrium vapor pressure of components, especially Cd, high separation coefficient of Zn and low stacking energy of crystal planes, lead to the existence of defects in the as-grown CZT crystals.In this paper, the central defects in CZT crystals and the reasons of their generation were analyzed. The defects in as-grow CZT crystals were observed through metallographic microscope and SEM. It was found that defects, such as dislocation, grain boundary, twin and impurity, etc. , existed in CZT crystals. Through IR, UV, electrical resistivity measurements and etching pits density calculation, it was found that as-grown CZT crystals had high defect density and low electrical resistivity , which make it impossible to be applied to fabricate room-temperature radiation detectors.To obtain high quality CZT crystals for detector fabrication, we carried out annealing process research on the CZT crystal. Based on the analysis of CZT crystal annealing mechanism and choosing different annealing parameters, the as-grown CZT crystals were annealed under different conditions. The CZT wafers before and after annealing were given annihilation lifetime spectrums measurement through Positron Annihilation Technology. Meanwhile, the electronic and optical properties of CZT wafers before and after annealing were measured by infrared...