Here, we report on experimental studies of the role of doping and co-doping on the properties of ZnO thin films deposited by radio-frequency diode sputtering at varying nitrogen content (0 divided by 100%) in the sputtering Ar/N-2 gas. Co-doping improved the crystalline structure, and ZnO: Al:N films maintain a c-axis texture in the direction of the surface normal. Depending on the N-2 content, the estimated crystallite size varies from 8 to 37 nm for ZnO: N and 21-33 nm for ZnO: Al: N. Nitrogen doping results in an increased absorption around the bandedge and the bandgap narrowing (E-g < 3.2 eV). (C) 2010 The Electrochemical Society. [DOI:10.1149/1.3459900] All rights reserved.