First-principles study of electronic and optical properties in wurtzite Zn_1-xCu_xO

We perform a first-principles simulation to study the electronic and optical properties of wurtzite Zn_1 - xCu_xO. The simulations are based upon the Perdew--Burke--Ernzerhof form of generalised gradient approximation within the density functional theory. Calculations are carried out in different concentrations. With increasing Cu concentration, the band gap of Zn_1 - xCu_xO decreases due to the shift of valence band. The imaginary part of the dielectric function indicates that the optical transition between O 2p states in the highest valence band and Zn 4s states in the lowest conduction band shifts to the low energy range as the Cu concentration increases. Besides, it is shown that the insertion of Cu atom leads to redshift of the optical absorption edge. Meanwhile, the optical constants of pure ZnO and Zn_0.75Cu_0.25O, such as loss function, refractive index and reflectivity, are discussed.