Co-doping of aluminium and gallium with nitrogen in ZnO films deposited by RFmagnetron sputtering

Abstract

N, (N + Ga) and(N + Al) doped ZnOfilms were deposited on c-plane sapphire substrates by RF magnetron sputtering at room temperature. Thesamples were characterized by their structural, surface morphological, compositionaland optical properties. The x-ray diffraction studies confirmed the co-doping of(N + Ga)and (N + Al) besides showing improvement in the crystallinity when compared with thesingle N doping. The surface of the films becomes rougher after co-doping. Thex-ray photoelectron spectroscopy and Rutherford back-scattering analysisindicate that the co-doping changes the chemical states and varies the amountof nitrogen (N) in ZnO. The amount of ‘N’ has been greatly increased for(N + Ga) co-doping, indicating that it is the best co-doping pair for p-type ZnO.Additionally, co-doping has increased the average visible transmittance (40–650 nm)and the optical band gap is shifted towards shorter wavelength. In the case of(N + Al) co-doping, the band gap becomes wider than that of undoped ZnO.