Effect of annealing on chemical, structural and electrical properties of Au/Gd2O3/n-GaN heterostructure with a high-k rare-earth oxide interlayer

The chemical, structural and electrical characteristics of a fabricated Au/Gd2O3/n-GaN heterostructure with gadolinium oxide (Gd2O3) as an insulating layer are explored by XPS, XRD and I-V techniques at room temperature and 400 °C annealing. XPS and XRD results reveal that the Gd2O3 films are formed at the interface. The electrical results of heterostructure are correlated with the conventional Au/n-GaN Schottky structure results. The as-deposited and 400 °C annealed heterostructures exhibited excellent rectifying behavior and very low reverse leakage current compared to the Schottky structure. Higher barrier height (BH) and on/off ratio are achieved for the heterostructure compared to the Schottky structure, which has led the barrier height modified by Gd2O3 insulating layer. Also, the results indicate that the BH slightly increases for the 400 °C annealed heterostructures. Further, the BH, ideality factor and series resistance are evaluated by Cheung's, Norde functions and ΨS-V plot and the values are found to be similar with one another that indicates their consistency and validity. In addition, the mechanism of the BH modulation could be explained by feasible energy level band diagrams. These findings indicate that the Gd2O3 films could be a favored dielectric material for the development of metal/insulating/semiconductor devices.