First-principles study of the effect of heavy Ni doping on the electronic structure and absorption spectrum of wurtzite ZnO

The band structures, densities of states and absorption spectra of pure ZnO and two heavily Ni doped supercells of Zn0.9722Ni0.0278O and Zn0.9583Ni0.0417O have been investigated using the first-principles plane-wave ultrasoft pseudopotential method based on the density functional theory. The calculated results showed that the band gap is narrowed by Ni doping in ZnO; this, is because the conduction band undergoes a greater shift toward the low-energy region than the valence band and because heavier doping concentrations lead to, narrower band gaps. Moreover, the optical absorption edge exhibits a redshift due to the narrowing of the band gap. Heavier doping concentrations leads to more significant redshifts, which is in agreement with the experimental results.