First principles study on band structure and optical properties of N-doped CuAlO2

The band structures, density of state and optical properties of undoped and N-doped CuAlO2 were investigated by density functional theory based on generalized-gradient approximation plus orbital potential. Impurity energy level was induced in the forbidden band of CuAlO2 after N doping. N-doped CuAlO2 shows p-type conductivity with direct band structure. Compared with the undoped CuAlO2, N-doped CuAlO2 has a smaller band gap which can be attributed to the downward shift of Cu-3p states in conduction bands and the stronger hybridization between Cu-3d and N-2p states. The optical performances were changed results in band gap narrowing that increases the probability of electronic transition from the impurity energy levels to the conduction band. Compared with undoped CuAlO2, static dielectric constant of N-doped CuAlO2 show increases and two new dielectric peaks appear at 0.929 eV and 13.305 eV, respectively. Refractive index, absorption, energy loss function and reflectivity were increased after N doping. Our results yield helpful insights on the use of CuAlO2 as photoelectric materials.