Electronic properties of barium chalcogenides from first-principles calculations: Tailoring wide-band-gap II-VI semiconductors

Electronic properties of barium chalcogenides were systematically studied using density functional theory computations, based on both generalized gradient approximation and local density approximation functionals. Different linear relationships are observed between theoretical band gap and 1/a(2) (where a is lattice constant) for barium chalcogenides containing oxygen and not containing oxygen, respectively. An abnormal behavior of electronic properties are found for compounds containing oxygen. The effects are attributed to the special properties of Ba-O bonds, which is different from other chemical bonds between barium and chalcogen atoms. Pauling electronegativity indicates that only Ba-O bonds are highly ionic bonds, and theoretical charge densities also show that electrons would be restricted to oxygen atoms when oxygen is in compound. The results reveal that it is possible to adjust the band gap significantly in barium chalcogenide by introducing oxygen atoms into its lattice for the gap tailoring of wide-band-gap II-VI semiconductors.