Phase Diagram, Melt Growth, and Characterization of Cd0.8Zn0.2Te Crystals for X-Ray Detector

In this study, the solidus curve of the Cd0.8Zn0.2Te homogeneity range was constructed from the partial pressure measurements by optical absorption measurements which provided the information of the melt-growth parameters to achieve crystals with the required electrical resistivity. The melt growth of Cd0.8Zn0.2Te crystals was then processed by directional solidification under controlled Cd overpressure. During the growth experiments, several procedures have been developed to improve the crystalline quality: (1) reducing the structural defects from wetting by HF etching of fused silica ampoule, (2) minimizing the contamination of impurities during homogenization, (3) promoting single-crystal growth by mechanical pulsed disturbance, and (4) maximizing electrical resistivity and minimizing Te precipitates by controlling Cd overpressure during growth and post-growth cooling. Additionally, the thermal conductivity, electrical conductivity, and Seebeck coefficient of a vapor-grown CdTe and two melt-grown Cd0.8Zn0.2Te crystals were measured between 190 °C and 780 °C to provide an in-depth understanding of the thermal and electrical conduction mechanisms of the crystals as well as the prospect of its thermoelectric applications.