P-Type Nitrogen-Doped ZnO Films Prepared by In-Situ Thermal Oxidation of Zn_3N_2 Films

P-type nitrogen-doped ZnO films are prepared successfully by in-situ thermal oxidation of Zn_3N_2 films. The prepared films are characterized by x-ray diffraction, non-Rutherford backscattering (non-RBS) spectroscopy, x-ray photoelectron spectroscopy, and photoluminescence spectrum. The results show that the Zn_3N_2 films start to transform to ZnO at 400^\circ\!C and the total nitrogen content decreases with the increasing annealing temperature. The p-type films are achieved at 500^\circ\!C with a low resistivity of 6.33 \Omega\cdot cm and a high hole concentration of +8.82 \times 10^17 cm^-3, as well as a low level of carbon contamination, indicating that the substitutional nitrogen (N_\rm O) is an effective acceptor in the ZnO:N film. The photoluminescence spectra show clear UV emissions and also indicate the presence of oxygen vacancy (V_\rm O) defects in the ZnO:N films. The p-type doping mechanism is briefly discussed.