Effect of Na contents on fabrication of p-type non-polar m-plane ZnO films

We report on the growth and characterization of Na-doped non-polar ZnO thin films, which have been prepared on m-plane sapphire substrates by plasma-assisted molecular beam epitaxy. The effects of Na contents on structural, morphological, electrical, and optical properties of Na-doped non-polar m-plane ZnO films are investigated. All the doped thin films have uniform m-plane orientation, which benefit from Na-doping. Na content plays a key role in determining the conduction of the ZnO films. An optimized result with a hole concentration of 5.3×1016 cm−3, a Hall mobility of 0.22 cm2 V−1 s−1, and a resistivity of 530 Ω cm is achieved at beam equivalent pressure of the elemental Na source of 8.7×10−9 Torr, and the films are electrically stable over several months.