Effect of deposition temperature on structural, morphological and optical properties of ZnTe thin films

This paper describes technological processes developed for less studied ZnTe thin films prepared by close space sublimation method, without an additional transport agent gas, for controlling their structural and optical properties. The enhanced oxygen incorporation depends on the source-substrate growth conditions. ZnTe thin films fabricated in the source-substrate temperature interval mentioned here crystallize in a cubic zincblende structure preferentially oriented along the [111] reflection plane. As the source temperature increases, the energy dispersive X-ray spectroscopy shows that the tellurium content increases, while the oxygen decreases. The values of the optical band gaps vary in interval from 2.21 eV up to 2.22 eV with variation of the source temperature, while variation of the substrate temperature leads to the band gap value decrease from 2.24 to 2.14 eV. The photoluminescence spectra of the ZnTe:O thin films are dominated by the red emission bands localized at 1.73 eV and 1.82 eV. This study will serve as a basis for future efforts to develop intermediate-band solar cells with improved conversion efficiency.