Characterization of secondary phases and other defects in CdZnTe

Semiconducting CdZnTe or "CZT" crystals are very suitable for use as a room temperature-based gamma radiation spectrometer. During the last decade, modifications in growth methods for CZT have significantly improved the quality of the produced crystals however there are material features that can influence the performance of these materials as radiation detectors. For example, various structural heterogeneities within the CZT crystals, such as, pipes, voids, polycrystallinity, and secondary phases (SP) can have a negative impact on the detector performance. In this study, a CZT material was grown by the modified vertical Bridgman growth (MVB) method with zone leveled growth in the absence of excess Te in the melt. Numerous SP were imaged using transmission IR at a volume % of 0.002. Samples from this material were analyzed using various analytical techniques to evaluate its electrical properties, purity and detector performance as radiation spectrometers and to determine the morphology, dimension and elemental /structural composition of one of the SP in this material. This material was found to have a high resistivity and good radiation spectrometer performance. It had SPs that were rich in calcium (Ca), carbon (C) and oxygen (O) (possibly CaCO3) or only C and O that were 5 μm or less in diameter. © 2010 Copyright SPIE - The International Society for Optical Engineering.