Correlation between grain orientation and carrier concentration of poly-crystalline In2O3 thin film grown by MOCVD

In this study, various In2O3 thin films were grown on c-plane sapphire substrates by metal-organic chemical vapor deposition via changing the growth parameters. The structural and electrical properties of the films were investigated by employing the X-ray diffraction (XRD), scanning electron microscopy, conductive atomic force microscopy (CAFM), and Hall Effect measurement. Results revealed that the investigated In2O3 thin films are bcc phase poly-crystalline with preferred orientation along the [100] or [111] direction. Moreover, the existence of two types of grains with different conductivities in the investigated In2O3 thin films was confirmed by CAFM measurement. Interestingly, a positive correlation was found between carrier concentrations and (222)/(400) XRD diffraction peak intensity ratios of the investigated In2O3 thin films. The mechanism of the positive correlation was explained by the difference in impurities concentrations between the two types of grains with the difference crystalline orientations.