Partial pressure of Cd in equilibrium with stochiometric melt and solid of (Cd0.8Zn0.2)Te between 300 °C and 1250 °C for melt growth

Abstract

The partial pressures over Cd0.8Zn0.2Te solid and melt were measured by the optical absorption technique on five optical cells loaded with four homogenized samples and one with as-grown crystal. From the measured partials pressures, the three-phase loops with five solidus and four liquidus points were established together with the Cd partial pressure over the melts. A series of crystal growth experiments by directional solidification of Cd0.8Zn0.2Te with controlled Cd overpressure, provided by Cd reservoir temperatures from 750 to 935 °C, were conducted. From the Te precipitates content observed by the IR micrographs, the correlation between the Cd reservoir temperature and the Cd0.8Zn0.2Te melt temperature, which resulted in the lowest precipitate density, was established. From the calculated masses of the elements in the vapor phase, the compositions of the condensed phases for each set of partial pressure data were derived. The correlation between the temperature of the Cd reservoir and the temperature of a stoichiometric Cd0.8Zn0.2Te sample, such that the equilibrium Cd overpressure is coexisted, have been established for the Cd0.8Zn0.2Te melt and the solid between 300 and 1250 °C. Using this information, the temperatures of the Cd reservoir and the Cd0.8Zn0.2Te sample can be programed during the melt growth to process intrinsic/stochiometric crystals. Additionally, the correlation on the equilibrium Cd overpressure environment for the Cd0.8Zn0.2Te solid can also be employed for the heat treatment of post-growth annealing to adjust the composition of the grown crystals toward stoichiometry.