FPLAPW study of the structural, electronic, and optical properties of Ga_2O_3: Monoclinic and hexagonal phases

摘要

Using the first principles full-potential linearized augmented plane-wave method within the local density approximation, we have studied the structural, electronic and optical properties ofGa_2O_3 in its ambient, monoclinic (beta) and high-pressure hexagonal (a) phases. It is found the both beta-Ga_2O_3 and alpha-Ga_2O_3 have an indirect band gap. The conduction band minimum (CBM) is located at GAMMA point for both phases, whereas the valence band maximum (VBM) is located at the M point for beta-Ga_2O_3 and at L point for alpha-Ga_2O_3. The calculated total and partial density of states are also presented. The analysis of the electron charge density shows that the Ga-O bonds have significant ionic character. The anisotropic optical properties are investigated by means of the complex dielectric function, which are explained by the selection rule of the band-to-band transitions. For the monoclinic phase, it is shown that the component with y-direction are more pronounced than that along the x and z.