Growth of phosphorus doped ZnO thin films by pulsed laser deposition

Undoped and phosphorus doped (1 and 3 mol%) ZnO (P-doped ZnO) films were grown on sapphire substrates by a pulsed laser deposition technique and then the phosphorus doping effect was investigated. Results of X-ray diffraction and scanning electron microscopy revealed that the phosphorus doping did not noticeably affect the microstructure and crystallinity of the undoped ZnO film. In the as-grown state, both of the P-doped ZnO films showed n-type conductivity rather with slightly more electron concentrations than that of the undoped ZnO film. For the 3 mol% P-doped ZnO film a significant decrease in the carrier concentration was observed at particular annealing temperatures (greater than or equal to 800 degreesC), still showing n-type conductivity. In contrast, in the case of I mol% P-doping, the variation in the carrier concentration was not significant under any annealing temperature. Our results suggest that a careful adjustment both of annealing temperature and of phosphorus doping content is required to control the electrical properties including the carrier concentration, resistivity and mobility in ZnO films.