Donor–acceptor pair luminescence of nitrogen doping p-type ZnO by plasma-assisted molecular beam epitaxy

We have grown N-doped p-type ZnO films by plasma-assisted molecular beam epitaxy. A dominant photoluminescence around 3.260 eV was observed at low temperature. By studying the dependence of photoluminescence on excitation density at 80 K, the emission around 3.260 eV can be attributed to a donor–acceptor pair transition. Time-resolved PL spectrum was also used to investigate the dynamics of the donor–acceptor pair recombination. The observed non-exponential decay curve was fitted by a fast component and long process. In long decay process, the curve was predicted to follow the power law t−1. Therefore it can be concluded that the emission at 3.260 eV in our sample is of a tunnel-assisted donor–acceptor pair nature.