Effect of rare-earth Pr₆O₁₁ insulating layer on the electrical properties of Au/n-GaN Schottky electrode and its chemical and structural characterization

An Au/Pr₆O₁₁/n-GaN metal/insulator/semiconductor (MIS) junction was prepared with a high-k praseodymium oxide insulator layer and probed its structural, chemical and electrical characteristics by XRD, TEM, XPS, I–V and C–V approaches. XRD, TEM and XPS examinations confirm the Pr₆O₁₁ film growth on n-type GaN surface. Electrical results demonstrate the fabricated junctions show a good rectifying nature with a low leakage current. The series resistance (R_S) and shunt resistance (R_Sh) were derived for the Au/n-GaN Schottky electrode (SE) and MIS junction. MIS junction possesses a higher barrier height (BH) compared to the Au/n-GaN SE, implying the insulator layer altered the BH. By employing Cheung’s, Norde and surface potential plots, the BH, ideality factor and R_S were evaluated and the results were comparable. Lower interface state density (N_SS) was obtained for the MIS junction than the SE, which confirmed that the Pr₆O₁₁ insulator layer plays a vital role in lowering the N_SS. Results demonstrated the Poole–Frenkel emission controls the current conduction mechanism in reverse-bias of both SE and MIS junction. Observations stated that the Pr₆O₁₁ thin film is a suitable high-k insulating material for the fabrication of GaN-based MIS devices.