p-Type Conductivity in N-Doped ZnO: The Role of the NZn-VO Complex

Although nitrogen-doped zinc oxide has been fabricated as a light-emitting diode, the origin of its p-type conductivity remains mysterious. Here, by analyzing the surface reaction pathway of N in ZnO with first-principles density functional theory calculations, we demonstrate that the origin of p-type conductivity of N-doped ZnO can originate from the defect complexes of N-Zn-V-O and N-O-V-Zn. Favored by the Zn-polar growth, the shallow acceptor of N-O-V-Zn actually evolves from the double-donor state of N-Zn-V-O. While N-Zn-V-O is metastable, the p-doping mechanism of N-Zn-V-O -> N-O-V-Zn in ZnO will be free from the spontaneous compensation from the intrinsic donors. The results may offer clearer strategies for doping ZnO p-type more efficiently with N.