CdMnTe offers several potential advantages over CdZnTe as a roomtemperature gamma-ray detector, but many drawbacks in its growth process impede the production of large, defect-free single crystals with high electrical resistivity and high electron lifetimes. Here, we report our findings of the defects in several vanadium-doped as-grown as well as annealed Cd 1Àx Mn x Te crystals, using etch pit techniques. We carefully selected single crystals from the raw wafer to fabricate and test as a gamma-ray detector. We describe the quality of the processed Cd 1Àx Mn x Te surfaces, and compare them with similarly treated CdZnTe crystals. We discuss the characterization experiments aimed at clarifying the electrical properties of fabricated detectors, and evaluate their performance as gamma-ray spectrometers.

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The authors believe that (Cd,Mn)Te can be used as a material for gamma-and X-ray detectors [1]. The investigations are concentrated on producing, by Bridgman method, of high quality (Cd,Mn)Te crystals with high resistivity (10 9 Ccm).The IR pictures of the interior of the monocrystalline (Cd,Mn)Te :V platelets cut parallel to the (111) crystal planes and annealed in various conditions are discussed.As grown, undoped (Cd,Mn)Te crystals are of p-type, which is related mainly to the Cd vacancies (acting as acceptors), present in the crystal after the process of growth. Doping with vanadium atoms, which acts as compensating centres, results in a semiinsulating material (Cd,Mn)Te: V. Proper annealing of the platelets in cadmium vapours at uniform temperature allows reducing of the number of cadmium vacancies and reducing the level of the vanadium doping, required for compensation.It turned out that annealing in cadmium vapours not only decreases the concentration of the native cadmium vacancies but also improves the quality of the crystal. Infra red observations of the interior of the samples show that annealing in the temperature gradient perpendicular to the platelet causes an additional effectmigration of the tellurium precipitates toward the side which is at higher temperature.The influence of various conditions of annealing in cadmium vapours on tellurium inclusions and precipitates is shown.