| Cd1-x Mnx Te（Cd Mn Te）, as an excellent ternary compound semiconductor material with advantages of wide band gap, high average atomic number and large density, can be a popular candidate of Cd Zn Te crystal for application in nuclear radiation detector. The Cd Mn Te radiation detector crystal will be widely applied in nuclear medicine, space science, airport security, nuclear waste monitoring and other nuclear technology fields. Thus, it is great significant to take the relevance research. Usually, the Vertical Bridgman（VB） method was widely adopted to grow Cd Mn Te crystals. However, because of the high growth temperature（1120℃）, solid-state phase transition and low stacking fault energy during the VB growth, many defects, such as twins, impurities, and inclusions, were observed in the Cd Mn Te crystal, which hinders the application of Cd Mn Te crystal in nuclear radiation detectors. In recent years, the Traveling Heater Method（THM）, combined with the advantages of liquid phase epitaxy and zone melting method, is believed to be a practical technique for growing high-quality large-volume Cd1-x Znx Te（Cd Zn Te） and Cd Mn Te single crystals. Compared to the VB method, THM is essentially a zone refine method with low growth temperature（800900℃）, which ensures the composition uniformity and low impurity density in the crystals. During the THM of Cd Mn Te crystal, it is great important to optimize the growth parameters and obtain a smooth and stable growth interface, to improve the quality of Cd Mn Te crystal. In this paper, the influence of temperature field on the properties of Cd Mn Te crystal grown by THM was investigated. The growth interface, composition distribution, impurities, Te inclusion, electrical properties and their relationship were characterized and analyzed, and the main research results were as follows:1. Three Cd Mn Te ingots with diameter of 31 mm and length of 130 mm were grown by the THM under three different temperatures field（950℃, 900℃, 850℃）. The growth interfaces of the crystals were analyzed. The shapes of all interfaces were concave with the curvature of about 0.34, 0.09 and 0.24, respectively. The growth interfaces grown under 900 ℃ was approximatively flat. In additional, some uncontrolled growth fronts were appeared in the growth interface grown under 950℃ and 850℃, and the roughness of the middle part of interface grown under 900℃ was smaller than the interface from 950℃ and 850℃. The smooth and stable growth interface under 900℃ were more favor for growing large size, high quality Cd Mn Te crystal.2. The influence of growth interface on Te inclusion and Mn composition distribution was investigated. The density and size of Te inclusion from crystal grown under 900 ℃ were low which due to the smooth and stable growth interface. Compared with the crystals grown under 950℃ and 850℃, the Mn composition axial and radial distribution in the crystal grown under 900℃ were more uniform.3. In the Cd Mn Te crystal grown by THM, the impurities in the end of ingots（Te-rich solvent） was higher than in crystals because of the zone refine effect. At the same time, the impurities in the crystal constantly decrease with the decline of growth temperature. Besides, the IR transmittances of these crystals from 500-4000 cm-1 were 51%, 65% and 54%, respectively. The smaller size and density of Te inclusion and lower impurities in the crystal can effectively increase the value of transmittance. The PL spectra of the crystal reveal that the crystal grown under 900℃ has（D0, h） peak without DAP peak and the half-peak width（FWHM） of（D0, X） peak is lower, which indicates that the crystal grown under 900℃ possessed higher crystalline quality.4. The electrical properties and energy response spectrum of Cd Mn Te: In crystals was investigated. The range of resistivity of the crystal grown with 950℃, 900℃ and 850 ℃ were 4.32′108-2.35′109 Ω×cm, 2.59′109-1.25′1010 Ω×cm and 1.28′109-4.55′109 Ω×cm, respectively. And all the crystals were n-type, and the crystal grown under 900℃ had the lowest carrier concentration and highest electronic mobility. Moreover, all the Cd Mn Te detectors had energy response to 241 Am at room temperature in the bias of 300 V, and the energy resolution were 17.2%ã€8.23% and 13.27%, respectively. |
