Effect of VI/II Ratio on Structure and Optoelectrical Properties of Zinc Oxide Thin Films Deposited by Metal-Organic Chemical Vapor Deposition

ZnO thin films with the c-axis orientation on the (0001) sapphire substrate were grown by metal-organic chemical vapor deposition. It was demonstrated that the VI/II precursor flow-rate ratio can influence strongly on the structure and opto-electrical properties. With the increasing VI/II ratio of 130:1, the full width at half maximum of (0002) peak in x-ray diffraction is only 0.184°, the near-band-edge emission enhances remarkably and the intensity ratio of the near-band-edge emission to the deep-level emission reaches 237:1 in the photoluminescence spectrum. At the same time, the resistivity and mobility increases to 3.28 x 10²Ω.cm and 25.3cm²V^-1s^-1. These facts indicates that the quality of the ZnO thin films could be improved by the increase of the VI/II flow rate ratio during the growth.