PNNL

Abstract

Cadmium zinc telluride (Cd1-xZnxTe or CZT) has proved to be a useful material for semiconductor gamma-ray spectrometers and other electro-optic devices. It is often grown Te-rich to optimize its electrical characteristics, but this off-stoichiometric growth leads to the formation of semimetallic Te precipitates in the semiconducting host crystal. These precipitates can impair device performance and their formation needs to be inhibited, if possible, during growth. Characterization of melt-grown CZT has shown that Te precipitates are often faceted. In this study, characterization of several particles of different shapes revealed that most of the Te precipitates were preferentially oriented with the {101}CZT||{-12-10}Te . A secondary orientation relationship was also observed as {11-1}CZT||{01-11}Te for one of the {111}CZT family of planes. One of the particles exhibited {110}CZT||{01-10}Te and {001}CZT||{0001}Te . Precipitates were often found on {111}CZT twin boundaries and, in these cases, it was possible to assign specific orientations with respect to the twin plane. The expected orientation of the {0001}-plane of Te aligned with the {111}-plane of CZT was not observed even though a good lattice match is predicted in ab initio models. Observations of strained and polycrystalline Te precipitates are also discussed with relevance to the ab initio model and to impacts on electronic properties.