First-principles calculation of electronic structure and polarization in ϵ-Ga₂O₃ within GGA and GGA + U frameworks

In this work, first-principles calculations of electronic structure and polarization property of ϵ-Ga₂O₃ have been carried out. To obtain an accurate energy bandgap, the GGA + U formalism is employed, where U refers to on-site Coulomb energy and is applied on the O atoms (U_O). Using appropriate lattice constants and numerical fitting, a value of 7 eV for U_O has been identified as an optimum choice, yielding a bandgap of 4.87 eV. The electron effective mass at the Γ point is found to be isotropic in nature and equals to 0.24m ₀. Finally, the GGA + U framework has been used for the calculation of spontaneous and piezoelectric polarization coefficients, which are extracted to be 23.3 μC cm^-2 and 79 μC cm^-2, respectively.