The properties of Cadmium Telluride are very sensitive to impurities. The growth method has also a strong impact on the material characteristics. Crystals grown by THM have good X-ray detector properties, while normal undoped Bridgman grown crystals do not detect. We have grown pure and doped samples by Bridgman and THM methods. As doping materials we used V, Zn and Cl, also in different combinations. The samples were characterized by several methods, including resistivity, TSC and nuclear detection measurements.

At very low temperature, below 4 K, the specific heat of PbFCI, PbFBr, and PbFT shows a classical behaviour with a T 3 temperature variation. The obtained Debye temperatures follow the Lindemann relation. Between 4 and 35 K, deviations from the T 3 law appear and are explained by means of two Einstein oscillators. These oscillators are linked to the low frequency optical phonons.Au dessous de 4 K, la chaleur specifique de PbFCI, PbFBr et PbFI presente un comportement classiquc de Debye. Les temperatures de Debye observees obeissent a la relation de Lindemann. Entre 4 et 35 K, des deviations a la loi en T 3 apparaissent et sont expliquees a I'aide de deux oscillateurs d'Einstein lies a des phonons optiques de basse frequence.

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The properties of Cadmium Telluride are very sensitive to impurities. The growth method has also a strong impact on the material characteristics. Crystals grown by THM have good X-ray detector properties, while normal undoped Bridgman grown crystals do not detect. We have grown pure and doped samples by Bridgman and THM methods. As doping materials we used V, Zn and Cl, also in different combinations. The samples were characterized by several methods, including resistivity, TSC and nuclear detection measurements.

Temperature measurements in a crystal growth ampoule of CdTe (Cadmium Telluride) are very difficult. Mathematical simulation is a very powerful tool to predict the behavior and temperature distribution during crystal growth. We applied this technique to the bulk growth of large single crystals of CdTe. The simulation revealed that for CdTe, it is possible to create a convex interface shape during growth, necessary for single crystal growth. The controlling parameter is the temperature profile along the ampoule. The temperature gradient is rather meaningless, as we can show with our simulations.We will present some crystals grown under good and bad thermal conditions.