Optical characterizations of Cd_1-XZn_XTe mixed crystals grown by vertical Bridgman-Stockbarger method

Cadmium zinc telluride is a tunable band gap II–VI compound semiconductor, which has received considerable attention due to its applications such as nuclear radiation detectors and industrial process monitoring. We have studied the optical properties of the ternary compound semiconductors Cd_1−xZn_xTe grown by vertical Bridgman-Stockbarger method in the whole range of zinc content 0 < x < 1. The crystal structure and material phase were characterized by X-ray diffraction (XRD) and Raman spectra. We measured the band gap energy for each of the samples by absorption and photoluminescence (PL) spectroscopy. From the experimental results we found that the band gap energy of Cd_1−xZn_xTe was located at around 1.457 eV with x = 0, and gradually shift to 2.174 eV for x equal to 1. The temperature-dependent absorption measurements to study the temperature dependence of band gap energy were also performed. Based on these analyses, the relationship between the band gap energies and the zinc content are verified and discussed. Furthermore, we will study the defect recombination mechanism by using temperature-dependent PL experiments.