A ZnMgO:N/ZnO/ZnO:Ga single hetero-junction light emitting diode structure on Al2O3 (11 (2) over bar0) substrate was fabricated by metalorganic vapor phase epitaxy. By using ZnMgO:N as a substitute for a ZnO:N top layer of a homojunction LED, improved rectifying current-voltage characteristics were obtained. Although the device had a heating problem and the luminescent area was partly in the ZnMgO:N layer, a sharp ultraviolet electroluminescence emission at 3.17 eV was successfully observed at room temperature.