Optical and electronic properties of defect chalcopyrite ZnGa2Se4: Experimental and theoretical investigations

The optical properties of ZnGa2Se4 single crystals obtained by gas transport reaction have been systematically explored using ellipsometry measurements and first-principles calculations. Analysis of X-rays diffraction pattern showed that the compound has a single-phase and tetragonal structure (space group (I4‾2 m)). The determined and calculated lattice parameters are in good agreement with each other. Spectral dependence of optical parameters; real εr and imaginary εi parts of the pseudodielectric function, absorption and reflectivity coefficients were obtained from the analysis of ellipsometry measurements. Absorption coefficient–photon energy dependency revealed the existence of direct band gap transitions with an energy of 2.81eV. This result is very close to the band gap obtained from our theoretical calculation. To explore the origins of the interband optical transitions theoretical group analysis was carried out.