Optical and electrical properties of highly nitrogen-doped ZnO thin films grown by plasma-assisted molecular beam epitaxy

Nitrogen-doped ZnO thin films with different nitrogen concentrations were fabricated by plasma-assisted molecular beam epitaxy. Hall effect measurements show p -type conduction for samples with low doping concentration. In highly doped ZnO, the p -type conduction converted to high resistance or unstable p -type behavior. This result indicates that highly doped samples are heavily compensated. In the low temperature photoluminescence spectrum, a donor-acceptor pair (DAP) emission band shows a strong redshift and broadening with increasing nitrogen doping concentration. The large shift of the DAP emission is explained by the Coulomb-potential fluctuation model related to compensated semiconductors.