Origin of p-Type Doping in Zinc Oxide Nanowires Induced by Phosphorus Doping: A First Principles Study

We investigated the geometric and electronic properties and doping efficiency of phosphorus-doped zinc oxide nanowires along the [0001] direction using the first-principle calculation. For isolated point defects, the substitutional and vacancy defects prefer the edge of the nanowire, the Zn interstitial defects favor the tetrahedral site, and the most stable P and O interstitial defects have a dumbbell-like structure. A complex defect of P-Zn-2V(Zn) is formed by the combination of a substitutional P at a Zn site (P-Zn) and two Zn vacancies (V-Zn), and it prefers the edge site. We found that P-Zn defects could be effective donors while V-Zn and P-Zn-2V(Zn) defects could be effective acceptors. The P-Zn defects have low formation energies and high concentrations under the Zn- and P-rich conditions, and they can lead to n-type ZnO nanowires. The V-Zn defects have low formation energies and high concentrations under the O- and P-rich conditions. The V-Zn defects can greatly suppress the P-Zn defects. V-Zn and P-Zn-2V(Zn) defects can lead to p-type ZnO nanowires under the O- and P-rich conditions.