Preparation and characterization of Mg, Al and Ga co-doped ZnO transparent conductive films deposited by magnetron sputtering

Mg, Al and Ga co-doped ZnO (AGMZO) thin films were deposited on flexible substrates by rf magnetron sputtering using ceramic targets at room temperature. The effect of Mg content on structural, morphological, electrical and optical properties of the films was investigated in detail. X-ray photoelectron spectroscopy measurements indicated that the Mg content in the films was substantially consistent with that of corresponding targets. X-ray diffraction (XRD) results revealed that the films had the hexagonal wurtzite structure. The (0 0 2) preferred orientation of the crystallites detected by XRD suggested that the grains grew perpendicular to the surface of the film, which was confirmed by the cross-section image. The average transmittance in the visible range was above 82% for all the films. The lowest resistivity of 2.8 x 10(-3) Omega cm with carrier concentration of 1.54 x 10(20) cm(-3) and Hall mobility of 14.6 cm(2)/Vs can be obtained. The optical transmission spectra revealed that when the Mg concentration increased, the UV absorption edge moved toward the shorter wavelength direction and the optical band gap increased from 3.4 to 3.5 eV.