Homogenization of Te-rich grown ZnTe bulk crystals by annealing under Zn vapor

Zinc telluride (ZnTe) has immense potential for a variety of optical and electro-optical devices. However, the structural inhomogeneity originating from non-stoichiometric melt growth restricts the extensive application of ZnTe-based devices. In this work, we report the structural homogenization of Te-rich grown ZnTe bulk crystals by annealing under saturated Zn vapor. Te inclusions smaller than 10 μm are eliminated successfully by regulating the annealing temperature (873-953 K) and annealing time (50-250 h). Simultaneously, the concentration of zinc vacancies has decreased significantly after annealing, which was confirmed from the 10 K photoluminescence (PL) spectra. Based on the annealing results, a mechanism of eliminating Te inclusions in the ZnTe crystal was proposed, according to the processes of Zn atom diffusion and the reaction of Zn atoms with Te inclusions. The diffusion path is determined by Zn vacancies in the ZnTe crystal. Finally, the Zn atom diffusion coefficient in the temperature range from 873 K to 953 K is estimated to be 9.73 × 10 ^-8 to 2.33 × 10 ^-6 cm ² s ^-1 in view of the proposed model, with a diffusion activation energy of ∼2.21 eV.