Effects of Al content on properties of Al–N codoped ZnO films

N doped and Al–N codoped ZnO films were prepared by dc reactive magnetron sputtering with a series of metal–Zn targets having different Al contents. The best p-type electrical properties of codoped ZnO, such as carrier concentration of 2.52 1017 cm 3, resistivity of 28.3 V cm can be realized by using 0.4 at.% Al target. Results of Hall effect and X-ray photoelectron spectroscopy (XPS) measurements confirm that the presence of Al indeed facilitates the incorporation of N through formation Al–N bonds in codoped ZnO. Finally, a new judgement for codoping effect in ZnO is proposed tentatively: the best codoping effect can be realized when the codoped ZnO films possess a closest (0 0 2) d-spacing value to the nominally undoped ZnO.