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(285a) Segregation and Interface Shape Control During EDG Growth of CZT Crystals

Zhang, N., University of Minnesota
Yeckel, A., University of Minnesota
Derby, J. J., University of Minnesota

The availability of large, single crystals of cadmium zinc telluride (CZT) with uniform properties is key to improving the performance of gamma radiation detectors fabricated from them. In this presentation, we discuss the validation of our computational models by comparison with experimental zinc distributions via photoluminescence measurements of Burger (Fisk University) and Lynn (Washington State University) for a CZT crystal grown using the electrodynamic gradient-freeze (EDG) method.  Furthermore, we predict non-classical zinc distributions for crystals grown in larger-scale EDG systems using classical thermal growth profiles.   This surprising result is consistent with many prior growth outcomes where “anomalous” zinc distributions have been observed, quite different from the segregation behavior exhibited by traditional Bridgman growth systems. 

We follow with a novel analysis to optimize EDG growth profiles to promote the growth of CZT crystals with a uniformly convex interface shape.  Such interface shapes may be very beneficial toward reducing the probability of new grain formation, thus improving the single-crystal yield for a growth run.  We also demonstrate that growth under these optimized thermal profiles results in zinc composition that is much more uniform than achieved using classical profiles.  We make the case that these results can be put directly into practice using existing EDG growth systems.