Recent Advances in the Preparation of CdTe for Nuclear Detectors

The traveling heater method (THM) of growing CdTe with a tellurium solvent has been used toproduce single crystals with low carrier concentrations from which gamma-ray detectors have been fabricated. The use of Cl, Br, or I as compensating dopants in the CdTe has resulted in Mate, ial with improved ¿T products [(¿T)n ¿ 4 × 10-4 cm2/V and (¿T)p 8 × 10-5cm2/V]. The dopant was added to the tellurium solvent as the cadmium salt in concentrations of 100 to 500 ppm by weight of the solvent. The best results to date have been obtained with Cl. An analysis of the temperature distribution during THM shows that it is possible to obtain a flat isotherm which is necessary to propagate single crystals. Low speed rotation (1 to 5 rpm) promotes a more symmetrical thermal distribution and improwes the crystallinity of the CdTe.