Electronic structure and optical properties of Mg_xZn_1-xS bulk crystal using first-principles calculations

We perform the first-principles calculations within the framework of density functional theory to determine the electronic structure and optical properties of Mg_xZn_1-xS bulk crystal. The results indicate that the electronic structure and optical properties of Mg_xZn_1-xS bulk crystal are sensitive to the Mg impurity composition. In particular, the Mg_xZn_1-xS bulk crystal displays a direct band structure and the band gap increases from 2.05 eV to 2.91 eV with Mg dopant composition value x increasing from 0 to 0.024. The S 3p electrons dominate the top of valence band, while the Zn 4s electrons and Zn 3p electrons occupy the bottom of conduction band in Mg_xZn_1-xS bulk crystal. Moreover, the dielectric constant decreases and the optical absorption peak obviously has a blue shift. The calculated results provide important theoretical guidance for the applications of Mg_xZn_1-xS bulk crystal in optical detectors.