First-principles study of p-type nitrogen/aluminum co-doped zinc oxide

First-principles calculations have been performed to investigate the electronic structures and the defects formation energies of the pure and nitrogen/aluminum (N-A1) co-doped zinc oxide. The calculated results of the pure ZnO using LDA+U method show band gap and lattice parameters are in reasonable agreement with previous data. Incorporation of N into ZnO host induces distortions of the lattice. According to the results, the Fermi-level of Al doped ZnO shift upward into conduction band and show n-type conductivity, while codoped structures show p-type conductivity. The defects formation energies of Al doped structure on Zn-rich and O-rich conditions are low. When codoped with N, the complexes exhibit high defects formation energy on O-rich condition, indicating it is difficult to realize p-type ZnO in this case. On Zn-rich condition, the codoped structures display lower defects formation energies and show p-type conductivity. From hole carriers analysis, it is shown that the carriers in N-Al doped ZnO possess a better transfer character. All these results indicate that codoped ZnO structures are beneficial for the realization of p-type ZnO.