Microstructure, optical and electrical properties of Al-doped ZnO films grown by MOCVD

Al-doped ZnO films were grown on quartz substrates by MOCVD. A systematical and detailed study about the effect of Al content on structural, optical and electrical properties were discussed. XRD measurements revealed that the preferred orientation of ZnO films decreased with the increase of Al content. AFM images indicated that the TMA molecules or their decomposition products bringing down the surface activity of ZnO grains, and so grain growth is inhibited. By the band tail states and the quantum confinement effect, the UV emission peak initially red-shifted and then blue-shifted. All Al-doped samples demonstrated more than 80% of the optical transparency in the visible region. Low electrical resistivity of Al-doped ZnO films was obtained. However, due to defects and grain boundary scattering which caused by Al doping, the hall mobility is increased initially and then decreased.