Tuning barrier height and enhancing electrical properties of MOS heterojunctions using Fe2O3 doped MoO3 nanocomposite interlayer on Ni/Cr/n-GaN for optoelectronic devices

This study investigates the structural, chemical, and electrical properties of Ni/Cr/Fe₂O₃:MoO₃/n-GaN Metal-oxide-semiconductor (MOS) heterojunctions using multiple characterization techniques. Comprehensive characterization using XRD, XPS, SEM, AFM, and I-V measurements confirmed the successful deposition of Fe₂O₃:MoO₃ films on the n-GaN surface. XPS analysis confirmed the successful formation of the insulating layer and metal electrodes on GaN, with clear elemental peaks. Glancing XRD further validated the structural and compositional integrity of the materials. Surface morphology was examined using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The results confirmed that the insulating layer and the metal electrodes have smooth and uniform surfaces. Electrical characterization revealed that the MOS heterojunction exhibited rectifying behavior with low leakage current as compared to the Ni/Cr/n-GaN Schottky diode (SD). The series resistance was evaluated for both the SD and MOS heterojunctions, with the latter displaying a higher Schottky barrier height (Φ_b), indicating the influence of the insulating layer. Higher barrier height (Φ_b) was obtained for the annealed MOS (0.90 eV) than the as-deposited MOS (0.80 eV) and SD (0.77 eV). The values of Φ_b, ideality factor (n), and R_s were determined using Cheung's, Z(V) - V_d, F(V)-V, and Ψ_S-V methods, yielding consistent results. The annealed MOS heterojunction shows the highest conductivity among SD and MOS heterojunction. I-V analysis evaluates the Φ_b, while photocurrent and dark current measurements confirm its superior photoconductive response. These findings highlight the potential of Fe₂O₃:MoO₃ nanocomposites and the significant influence of annealing temperature on GaN-based MOS heterojunction, reinforcing their suitability for optoelectronic applications.