Preparation of ultra-high purity CdTe single crystals

High-purity and quality CdTe single crystals are very important for their basic study, as well as practical applications. For this reason, Cd was purified by vacuum distillation (VD) and overlap zone-melting (OZM) method, and Te was purified by normal freezing method. Refined Cd was evaluated by glow discharge mass spectroscopy (GDMS) and residual resistivity ratio (RRR) measurement and Te was evaluated by low-temperature photoluminescence (PL) spectra. Results showed that refined Cd and Te have the purity of 6N-up. Using the refined Cd and Te as starting materials, extremely high-purity CdTe single crystals were prepared by the traditional vertical Bridgman technique. The crystals were characterized by low temperature high-resolution PL spectroscopy. Only a sharp peak at 1.5896 eV was detected in exciton emission region. The full width at half-maximum (FWHM) is less than 0.31 meV. These results indicate that the CdTe crystals are of extremely high-purity and quality.