Homogeneity limits and nonstoichiometry of vapor grown ZnTe and CdTe crystals

Abstract

The homogeneity regions of zinc telluride ZnTe and cadmium telluride CdTe were studied by the “extraction” technique at 750–1365 K temperature range. It is shown that the homogeneity region of undoped ZnTe contains a stoichiometric composition. The existence of wurtzite-based ZnTe at high temperatures was proven and its lattice parameters were determined. A scheme of the 3C–2H polymorphous transition for ZnTe compounds is proposed in which the transition is followed by peritectic reactions at both the Te-rich and Zn-rich sides. In the case of CdTe, the solidus line near the melting point demonstrated an anomalous behavior, which could be explained in terms of the high-temperature polymorphous transition, but the polymorph was not fixed because of the low transition energy. The undoped ZnTe and CdTe single crystals were obtained by the Markov–Davydov vapor growth technique under pressures close to congruent sublimation conditions in the temperature range 1170–1320 K. The nonstoichiometry and impurity distribution in 60 mm diameter ZnTe and 100 mm diameter CdTe vapor grown crystals were examined.