FPLAPW study of the structural, electronic, and optical properties of Ga2O3: Monoclinic and hexagonal phases

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 of Ga2O3 in its ambient, monoclinic (β) and high-pressure hexagonal (α) phases. It is found the both β-Ga2O3 and α-Ga2O3 have an indirect band gap. The conduction band minimum (CBM) is located at Γ point for both phases, whereas the valence band maximum (VBM) is located at the M point for β-Ga2O3 and at L point for α-Ga2O3. 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.