Bulk growth of uniform and near stoichiometric cadmium telluride

Crystal growth of bulk cadmium telluride (CdTe) ingot with 64 mm diameter and 75 mm height was accomplished in a modified vertical Bridgman configuration with the aim of achieving minimal nonstoichiometry related second phases (SP) defects such as inclusions and precipitates. As-grown crystal wafers were characterized with respect to infrared microscopy, bulk resistivity, low-temperature photoluminescence (PL) and foreign impurity concentration. Except for grain boundaries and twins, the wafers were found to be completely free of SP of sizes >1 μm and the distributions at different parts of the grown boule were found to be identical. Star shaped inclusions were observed at some places near the mid-section of the ingot, which were tentatively identified as Cd inclusions. At room temperature, the crystal exhibited high bulk resistivity values of 107-108 Ω cm, which was found to be in conformity with the low density of nonstoichiometric defects. GDMS results indicated that the concentration of unintentional impurities was low enough for the electrical behavior to be explained uniquely on the basis of native defects.