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The conduction types of Na-doped ZnO films with different Na contents were investigated by repeated Hall-effect measurements and rectification behaviour of ZnO: Al/ZnO: Na homojunctions. A p-type ZnO: Na film with a resistivity of 13.8–19 Ω cm, Hall mobility of 0.12–1.42 cm 2 V− 1 s− 1 and hole concentration of 4.78× 10 17–4.66× 10 18 cm− 3 was achieved, and it was electrically stable over 9 months. The effect of the Na concentration on the conductivity of ZnO films was discussed tentatively from the results of x-ray diffraction and Hall-effect measurements as well as from the viewpoint of Madelung energy. Electroluminescence was obtained at 160 K from the optimized p–n homojunction on the silicon substrate.