The band structure, density of states, Mulliken population analysis and optical properties of Ga-Eu codoped ZnO structure were calculated by using the first principles method based on density functional theory. The results reveal that the calculated lattice constants and band gaps agree well with the experimental values. The incorporation of Ga and Eu atoms provide a large amount of free carriers, enhancing the conductivity of the system. At the same time, the Fermi level enters the conduction band and exhibits n-type conductivity. Besides, the density of states show that the impurity band introduced by the 4f state of Eu appears at the Fermi level, and the 4p state and the 4s state of Ga atom also contribute to the bottom of the conduction band. What's more, the Mulliken atomic and bond populations of Ga-Eu codoped ZnO indicates that the doping of Ga and Eu atoms enhances the ionicity of the bonds. Lastly, the Ga and Eu atoms cause the peaks of the real and imaginary parts of the dielectric function to shift to the low energy region, and the absorption and reflectivity increase in the visible light region.
