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 degrees 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 degrees 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 degrees 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. (C) 2020 Elsevier B.V. All rights reserved.