Recent success in the synthesis of p-type ZnO by codoping method results in the fabrication of ZnO-based p-n homojunction, promoting the comprehensive applications in electronics. The ceramic bulk which consists of ZnO-2 wt% Al2O3 is used as the target using a RF magnetron sputtering system in this study with various volume ratios of N2O as a reactive gas at the substrate temperature of 500 degrees C to obtain the Al-N codoped ZnO films and the structure, surface morphologies, electrical properties and transmittance of thin films are analyzed. In this study, all prepared films show a ZnO wurtzite structure with a preferred orientation of (0 0 0 2). As 30% volume ratio N2O is introduced, the Al-N codoped ZnO film exhibits the best p-type conductivity with a resistivity of 2.6 +/- 0.8 Omega cm, a hole concentration of (2.5 +/- 0.2) x 10(17) cm (3) and a Hall mobility of 9.6 +/- 0.4 cm(2)/V s. However, excessive N2O turns the conduction type from p-type to n-type. With the addition of N2O, the absorption edge of the Al-N codoped ZnO film exhibits a red-shift in the spectrum. Additionally, the fabricated ZnO-based homojunction shows a rectifying I-V curves, further demonstrating the successful preparation of the p-type Al-N codoped ZnO film. (C) 2008 Published by Elsevier B.V.