Effect of Cu/Al doping on electronic structure and optical properties of ZnO

The stability, electronic structure, conductivity and optical properties of Cu/Al doped ZnO in the condition of different concentrations and different positions were studied by using the first-principles generalized gradient approximation plane-wave pseudopotential method combined with Hubbard U correction based on density functional theory. Geometric optimization and energy calculations for the original structure of pure ZnO, Zn0.96875R0.03125O (R replaces Cu or Al) and Zn1-x-yCuxAlyO (x, y = 0.03125, 0.03125; 0.0625, 0.03125 and 0.03125, 0.0625). The results show that the co-doped systems are more stable than single-doped, and each of the systems is easier to form under 0-rich conditions. When doping at the same concentration, the volume of the system with different impurity atoms on the same horizontal plane is small. In this paper, the co-doping can greatly reduce the band-gap of ZnO, so that the absorption edge of each system is red-shifted, the absorption of Zn0.90625Cu0.0625Al0.03125O in visible light is the strongest. The carrier mobility and conductivity of each system were calculated by the relative quantity of carriers and the effective mass. It is found that co-doping is more beneficial to the conduction than single-doping, and the influence of the concentration of Al on the conductivity of the system is larger than that of Cu.