论文部分内容阅读
The effects of annealing on the chemical states of N dopant, electrical, and optical properties of N-doped ZnO film grown by molecular beam epitaxy (MBE) are investigated. Both the as-grown ZnO:N film and the film annealed in N2 are of n-type conductivity, whereas the conductivity converts into p-type conductivity for the film annealed in O2. We suggest that the transformation of conductivity is ascribed to the change in ratio of the N molecular number on O site (N2)o to the N atom number on O site (No) in ZnO:N films under the various anneaied atmosphere. For the ZnO:N film annealed in N2, the percentage content of (N2)o is larger than that of No, i.e. the ratio > 1, resulting in the n-type conductivity. However, in the case of the ZnO:N film annealed in O2, the percentage content of (N2)o is fewer than that of No, i.e., the ratio < 1, giving rise to the p-type conductivity. There is an obvious difference between low-temperature (80 K) PL spectra of ZnO:N film annealed in N2 and that of ZnO:N film annealed in O2. An emission band located at 3.358eV is observed in the spectra of the ZnO:N film after annealed in N2, this emission band is due to donor-bound exciton (D0X). After annealed in O2, the PL of the donor-bound exciton disappeared, an emission band located at 3.348eV is observed, this emission band is assigned to acceptor-bound exciton (A0X).