Electronic structure of cadmium selenogallate CdGa2Se4 as studied using ab initio calculations and X-ray photoelectron spectroscopy

Electronic properties of cadmium selenogallate CdGa2Se4, a very promising electro-optical material, were studied both from theoretical and experimental points of view employing the ab initio band-structure augmented plane wave + local orbitals (APW + LO) method with the WIEN2k code and X-ray photoelectron spectroscopy (XPS). The present APW + LO calculations reveal that the Se p-like states are the dominant contributors into the top of the valence band of CdGa2Se4, while the bottom of the band is dominated by contributions of the Cd d-like states. Additionally, the bottom of the conduction band of the compound under consideration is dominated by contributions of the Ga s-like states. The present calculations render that the valence-band maximum and conduction band minimum in CdGa2Se4 are located at Γ resulting in a direct energy gap. The imaginary part of the electronic dielectric function ɛ(ω) was also calculated for the compound under consideration based on its band-structure data. The ɛxx(ω) and ɛzz(ω) components of the imaginary part of the electronic dielectric function reveal a considerable anisotropy in CdGa2Se4. The XPS valence-band spectrum of CdGa2Se4 has been derived and the binding energies of core-level electrons of the constituting atoms of the compound have been measured.