First-Principles Investigation of Electronic, Half-Metallic, and Optical Properties of Ti-Doped MgTe Semiconductors with Various Concentrations of Dopant

Abstract

The electronic, magnetic, and optical properties of Ti-doped semiconductors Mg_1−xTi _x Te at concentrations of x = 0.25, 0.50, and 0.75 have been investigated in the framework of density functional theory. Spin-polarized calculations of the electronic structure of Mg_1−xTi _x Te revealed that these compounds are half-metallic ferromagnetic materials with 100% spin polarization at the Fermi level. Large half-metallic gaps of 1.69 eV, 1.18 eV, and 0.98 eV were obtained for these compounds with Ti concentration of 0.25, 0.50, and 0.75, respectively. In addition, the origin of the half-metallic gap in Mg_1−xTi _x Te is discussed based on the partial density of states. It is found that hybridization between Ti-3d and Te-5p states and the large exchange splitting of the Ti-3d states are responsible for the half-metallic property of Mg_1−xTi _x Te compounds. The Curie temperatures of Mg_0.5Ti_0.5Te and Mg_0.25Ti_0.75Te were predicted to be 572 K and 959 K, respectively, within the mean field approximation. The appropriate half-metallic properties of Mg_1−xTi _x Te (x = 0.50 and 0.75) make them appropriate electronic materials for use in spintronics applications. The optical properties of pure and Ti-doped MgTe semiconductors, such as the dielectric function, extinction coefficient, absorption coefficient, reflectivity, and optical conductivity, were also considered. It was found that Ti doping considerably changed the optical properties of the MgTe semiconductors, especially at lower frequencies, such that these materials can be used in optical devices such as photodetectors and solar cells over wider ranges of frequency than corresponding undoped material.