Using a NiZn solid solution layer to produce high-barrier height Schottky contact to semipolar (20–21) n-type GaN

Abstract

Formation of high barrier height Schottky contacts to semipolar (20–21) n-GaN was realized by using a NiZn solid solution (NiZn s.s.) layer. The X-ray diffraction (XRD) and X-ray photoemission spectroscopy (XPS) results exhibited the creation of Ni-oxides and N-gallide phases when the contact samples were annealed at 650 °C. The XPS Ga 2p core levels attained from the NiZn s.s./GaN interface underwent a shift toward lower energies upon annealing. STEM element mapping and XRD results illustrated Ga outdiffusion in the 650 °C-annealed sample. The current-voltage (I–V) plots of the samples revealed that the reverse leakage characteristics were improved with an increase in the annealing temperature from 0 to 650 °C. The ideality factors and Schottky barrier heights (SBHs) assessed by the I–V method were in the range 2.13–2.73 and 0.54–0.68 eV, respectively. With increasing annealing temperature, the ideality factor decreased, while the SBH increased. It was also shown that the barrier inhomogeneity and capacitance-voltage methods produced much larger SBHs of 0.61–1.54 eV than the I–V method. Based on the XRD, STEM, and XPS analyses, the dependence of the SBHs on the annealing temperature is described.