Electronic and optical properties of mixed anion layered oxychalcogenide semiconductors: An ab initio study

A full potential linear augmented plane wave method within the density functional theory is used to calculate the electronic and optical properties of layered compounds of LaCuOCh (Ch=S, Se, Te) and their alloys LaCuOCh_0.5Ch_0.5^′(Ch, Ch^′=S, Se, Te). These compounds are found to be direct band gap semiconductors and may have a high p-type electrical conductivity, which can be tuned by proper alloying. The dielectric functions and optical constants—refractive index, absorption coefficient, and real part of optical conductivity of these materials—are calculated. The present study shows by changing the chalcogenides in the alternate covalent Cu–Ch layers that one can control the electrical conductivity and optical emission in these oxychalcogenide semiconductors.