Doping efficiency, optical and electrical properties of nitrogen-doped ZnO films

Doping efficiency and optical and electrical properties of the N-doped ZnO films grown on c-sapphire were investigated. An anomalous Raman mode at 275 cm(-1) was observed in the films grown at high Zn temperature, which implied that the films have a large number of defects induced by high N concentration. The intensity ratio of the donor-acceptor pair (DAP)/donor-bound exciton (DX) increases with increasing Zn temperature; this was attributed to the increase of N concentration. The films exhibit a conversion from n-type to p-type conductivity with increasing Zn temperature, and reproducible p-type conductivity was obtained at the Zn temperature of 255 degrees C. This study offers a simple and effective route to enhance the N solubility in ZnO films and confirms that the anomalous Raman mode at 275 cm(-1) was related to substitution of N for O site (N-O) and not related to substitution of N-2 for O site (N-2)(O). (C) 2011 American Institute of Physics. [doi:10.1063/1.3579454]