The influence of Ar/O-2 gas on phosphorus-doped ZnO (ZnO:P) thin films deposited by radio frequency magnetron sputtering was studied. As the partial pressure of O-2 increased in the Ar/O-2 sputtering gas, the structure of ZnO: P changed from nanorods to a smooth thin film. The electron concentration of the thin film was also decreased due to the reduction in oxygen vacancies that act as donors. Photoluminescence spectra of ZnO: P thin films also showed a reduction in the intensity of the deep level emission peaks, due to the reduction in native defects related to the oxygen vacancies as the O2 partial pressure was increased. The ZnO: P thin films grown under an Ar/O-2 gas ratio of 1:3 showed p-type characteristics after a rapid thermal annealing (RTA) activation process. The p-type ZnO:P showed a resistivity of 0.05 Omega cm, a mobility of 4.19 cm(2)/V s, with a hole concentration of 1.7 x 10(18) cm(-3). (c) 2006 The Electrochemical Society.