Structural and optical property characterization of epitaxial ZnO:Te thin films grown by pulsed laser deposition

We have investigated the Te atom incorporation, solubility, structural features and the corresponding optical property of epitaxial ZnO:Te thin film grown on c-plane sapphire by pulsed laser deposition. Incorporation of Te at the oxygen (TeO) or zinc (TeZn) site can be controlled through the deposition scheme to transfer Te during the film growth. Solubility of Te at the oxygen site is strongly dependent on the growth temperature and a maximum of ~4 at% Te is obtained at 400 °C with the film remained to be in epitaxial form. Lowering the temperature further increases Te incorporation but films turn out to be amorphous. For Te at the Zn site a maximum of ~3.4 at% is achieved with the film to be in the epitaxial form with tilt and phase separation is observed beyond this composition. Band gap decreases with Te incorporation both in the oxygen and zinc sites but decrease in band gap is found to be pronounced and composition dependent for the former case.