Plasma and annealing treatments to form height-barrier Ni-based Schottky contact to n-GaN

We investigated the combined effects of plasma and annealing treatments on the electrical and interfacial reactions of Ni/Au Schottky contacts on n-GaN for high-efficiency electronic and optoelectronic devices. Thermionic emission (TE)-based ideal current-voltage model showed that the Schottky barrier heights (SBHs) ranged from 0.68 to 0.92 eV and the ideality factors were in the range of 1.16-2.15. On the other hand, inhomogeneity model and capacitance-voltage characteristics gave similar SBHs in the range of 1.11-1.45 eV. X-ray photoemission spectroscopy (XPS) results displayed that annealing caused the Ga 2p core level to shift toward lower energies by 0.17-0.18 eV, while plasma treatment induced the Ga 2p core level to shift toward higher energies by 0.12 eV. The XPS Ni 2p core level results exhibited that annealing samples at 600°C gave rise to the formation of NiO and Ni₂O₃ in addition to Ni₃Ga₄ and Ni₃Ga interfacial phases, which were confirmed by X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM) results. Based on the XPS, XRD, and STEM results, the annealing and plasma-treatment-induced increase in the SBHs is described and discussed.