The reliability of p-type ZnO thin films obtained by phosphorus implantation, using plasma-immersion ion implantation, followed by rapid thermal annealing is reported. Also reported is the fabrication of a ZnO-based homojunction light-emitting diode. Low-temperature photoluminescence measurements after six months showed a dominant free electron-to-acceptor peak for samples annealed at 900 and 1000° C, confirming the formation of p-type films. Room-temperature electroluminescence spectra for the p-ZnO:P/n-ZnO homojunction diode revealed ultraviolet (UV) emission at 3.18 eV; however, the dominant peak was observed at 1.8 eV because of a deep-level defect peak. Achieving dominant UV emission requires further optimisation of the device structure. © The Institution of Engineering and Technology 2014.