N-Al codoped p-type ZnO thin films have been characterized. The resistivity can be lowered to 2.6 Omega cm, and the p-type conductivity is reproducible and stable. The co-doped films possess good crystal quality with high (002) orientation and prominent UV emission around 3.14 eV at room temperature. The two-layer-structure ZnO p-n homojunctions were fabricated on a sapphire substrate by depositing the N-Al codoped p-type ZnO film on the Al-doped n-type ZnO film. The current-voltage (I V) characteristics exhibit the inherent and acceptable rectifying behavior for the p-ZnO:(N,Al)/n-ZnO:Al homojunctions. (c) 2005 Elsevier B.V. All rights reserved.