Comparison of CdZnTe crystals grown by the Bridgman method under Te-rich and Te-stoichiometric conditions and the annealing effects

Two categories of CdZnTe (CZT) wafers were grown, one by the modified vertical Bridgman method (MVBM) under Te-rich and the other under Te-stoichiometric conditions. The effects of annealing in saturated Cd vapor on CZT properties such as precipitate, infrared (IR) transmission, etch pit density (EPD) and full-width at half-maximum (FWHM) value of X-ray rocking curve were systematically discussed. As-grown CZT wafers grown under Te-rich conditions contain large-size Te precipitates with density of high-103–low-104 cm−2 and IR transmission less than 60%. The micron-size Te precipitates were entirely removed and IR transmission was increased to over 60% after annealing based on the Cd-diffusion-induced thermomigration mechanism. In comparison, as-grown wafers grown under Te-stoichiometric conditions contain Cd precipitates with density of high-105 cm−2 and IR transmission ∼60%. After annealing, the precipitate density was reduced to low-104 cm−2 and IR transmission exceeded 60%, indicating a simple and yet novel approach for eliminating Cd precipitates. The FWHM and EPD of CZT wafers were not significantly influenced by annealing. In short, crystal growth under Te-rich conditions was proved to be a practical technique for producing high-quality CZT.