Electronic structure of the transparent p-type semiconductor (LaO)CuS -: art. no. 245211

(LaO)CuS with a layered structure is a transparent p-type semiconductor (band gap = 3.1 eV), which gives an excitonic absorption/emission near the band edge even at room temperature. We examined the electronic structure of this material by photoemission and inverse photoemission spectroscopy and considered the nature of the electronic structure by comparing the photoemission spectra with the band structure calculated by the full-potential linearized augmented plane-wave method within the local-density approximation. It was proved that the top of the valence band is primarily composed of well-hybridized states of Cu 3d and S 3p states, while the bottom of the conduction band consists mainly of Cu 4s states. The band gap of (LaO)CuS was found to be a direct-allowed transition type through the analysis of the symmetry of these states. It was also found that the dispersion of the valence band is relatively large due to the considerable hybridization of Cu 3d and S 3p states. This dispersed valence band is responsible for the emergence of p-type electrical conduction in this material. On the other hand, the dispersion of the conduction band is rather small, probably because of the layered structure, in comparison with typical n-type conducting materials, This small dispersion of the conduction band leads to the wide band gap and high stability of excitons in (LaO)CuS.