Analysis of the chemical states and microstructural, electrical, and carrier transport properties of the Ni/HfO/GaO/n-GaN MOS junction

This paper investigates the effect of gallium oxide (GaO) and hafnium dioxide (HfO) thin films as interlayers between the Ni and n-GaN semiconductor on the electrical characteristics of the Ni/n-GaN Schottky junction (SJ). The X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) results confirmed that GaO and HfO films were formed on the n-GaN semiconductors. The electrical and transport carrier properties of the Ni/HfO/GaO/n-GaN metal/oxide/semiconductor (MOS) junction were obtained via current–voltage (I–V) measurements and compared with Ni/n-GaN Schottky junction in the voltage range from − 5 V to + 5 V at room temperature. In contrast to the SJ, the MOS junction displayed a superior rectifying nature and a lower reverse leakage current. The barrier height (Φ) and ideality factor values of the SJ and MOS junctions were estimated to be 0.58 eV and 1.21, and 0.75 eV and 1.06, respectively. A higher Φ was attained for the MOS junction compared to the SJ, which enabled the GaO and HfO interlayers to alter Φ. The Φ values are derived from the I–V, Hernandez, Cheung, and surface potential methods and the derived values were comparable to one another, which indicates their consistency and validity. The density of the interface state (N) of the MOS junction decreased compared to SJ, which indicates that the interlayers influence the N of the SJ boundary. The forward bias log (I) − log (V) curve of the SJ and MOS junction revealed the ohmic nature in low-voltage regimes and space-charge-limited conduction in high-voltage regimes. The results show that the Poole–Frenkel emission dominates the reverse leakage current of the SJ and MOS junction. These outcomes indicate that GaO and HfO films can be chosen as dielectric materials in the construction of MOS devices.