Istituto dei materiali per l'elettronica ed il magnetismo     
Zappettini A., Marchini L., Zha M., Zambelli N., Calestani D., Zanotti L., Mosca R., Gombia E., Zanichelli M., Pavesi M., Auricchio N., Caroli E. Growth and characterization of CZT crystals by the vertical Bridgman method for X-ray detector applications. In: IEEE 2010 NSS/MIC/RTSD (Knoxville, Tennessee, USA, 30 October - 6 November 2010).
CdZnTe crystals are largely employed for the preparation of X and gamma ray detectors. However, in spite of the efforts, the yield of high quality material is still low due to the difficulties to obtain high purity large single crystals with a low concentration of defects such as tellurium precipitates. In this frame, the authors have grown crystals by the standard vertical Bridgman method and by the boron oxide encapsulated vertical Bridgman method in order to compare the results obtained in terms of single crystal yield, purity, detector performances. With this purpose, the grown crystals are characterized by many techniques, such as photoluminescence, IR mapping, current-voltage measurements, off-stoichiometry determination, photoconductivity. Moreover, the X-ray response of the obtained detectors is studied. In particular, the not uniform zinc distribution that derives from the well-known zinc segregation has been used to analyze the growth interface shape by means of luminescence mapping. The results show that boron oxide is effective in maintaining a convex interface of the growing crystal up to the end of the growth. Improvements of the mobility-lifetime product have been observed in crystals grown without the use of boron oxide as a result of the improved purity of the growth process.
Subject CdZnTe
X-ray detectors

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