Theoretical investigation of the electronic structure and optical properties of zinc-doped magnesium oxide

In this work, the electronic structure and optical properties of Mg₁₋ₓZnₓO ( 0≤ x ≤ 0.5 ) are investigated within the framework of the density functional theory (DFT), the GW method, and the Bethe–Salpeter equation (BSE). We find that zinc doping can lower the band gap of pure MgO via the Zn 4s states near the Fermi level and reduce the lattice symmetry, both of which will affect the optical properties. The energy of the first absorption peak decreases as the concentration of zinc increases, so are the exciton energy and binding energy of the lowest excited state. The results nicely fit to published experimental results and are compared to those of the simple hydrogen-like atom model for excitons. As the lowest excited state is closely related to light emission at that energy according to Kasha’s rule, zinc doping will lower the light emission energy of pure MgO, while still exhibiting an exciton binding energy much higher than that of kBT at room temperature. This means that Mg₁₋ₓZnₓO materials are perfectly suited for optoelectronic devices operating in the deep blue and near-ultraviolet (UV) range.