The anisotropic optical properties of different polytypes (ε, β, δ, γ) of GaSe lamellar materials

In this paper, we have calculated the optical properties of the different polytypes of GaSe lamellar materials. The calculations are based on the DFT method and is performed using the CASTEP code. All optical properties have been studied in a domain that extends energetically from 10 meV to 35 eV and have been measured for a polarization // and ⊥ with the c axis. A strong anisotropic was observed, which indicates that the optical properties of the GaSe material are essentially determined by the symmetry of a single layer, exactly by the symmetry resulting from the stacking of the layers. Moreover, the absorption starts in the UV–vis spectral range, the peaks appear in the UV range. The refractive index values are n xx  = 2.54, 2.55, 2.88, 10.85, n zz  = 3.90, 3.90, 3.26, 11.73 for e , β , γ , δ , respectively at zero photon energy. Furthermore, we notice that the optical properties of different polytypes (e , β , δ , γ ) of GaSe lamellar materials are obtained both in the ultraviolet field or in the visible domain are significant and give a strong argument for the use of these materials in various applications, namely photovoltaic cells, nanoelectronic, optoelectronic, optical fiber and photo-catalytic applications.