Study of the anomalous zinc distribution in vertical Bridgman grown CdZnTe crystals

The exploitation of CdZnTe crystals for the preparation of X- and gamma-ray detectors is still limited by the low yield in the production of high quality material. Twins and grain boundaries are still present in the state of the art melt-grown crystals, due to the difficulty to implement seeding procedures. In this paper, the zinc content of several CdZnTe crystals is analyzed in detail with the purpose of studying the phenomena occurring in the first part of growth. It is found that both the obtained experimental data as well as the ones reported by several other authors cannot be explained in terms of the usually reported model, based only on the effects of supercooling. Alternative explanations that take into account the possibility of nucleation from different sites and the possible effects of zinc thermodiffusion are suggested. These observations are very important in view of implementation of new growth configurations for obtaining larger single crystal yield.