Analysis of electrical properties in Ni/GaN schottky contacts on nonpolar/ semipolar GaN free-standing substrates

This work focuses on the electrical properties of Ni/n-GaN Schottky barrier diodes (SBDs) fabricated on GaN bulk substrates with different crystal orientations. For the SBDs on a-plane, m-plane, and s5-plane GaN, the Schottky barrier heights (SBHs) exhibited magnitudes of 0.65 eV, 0.69 eV, and 0.75 eV, respectively. The relatively small SBH of a-plane devices results in a relatively larger reverse leakage current than that of m-plane and s5-plane. In addition, the carrier concentrations extracted by C-V characteristics are comparable for the GaN substrates with different crystal orientations. The temperature-dependent I-V characteristics indicate how the barrier inhomogeneity of the Ni/GaN Schottky contacts on the a-plane GaN is smaller than the others. Based on the XPS spectra results, the discrepancy in Schottky contact characteristics stems from the different polarization charges and/or surface oxides of the different crystal planes. The low GaOx density on a-plane GaN surface contributes to the minimum barrier inhomogeneity of the corresponding SBD devices. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study focuses on the electrical properties of Ni/n-GaN Schottky barrier diodes fabricated on GaN bulk substrates with different crystal orientations. The results show that the crystal orientation of the GaN substrate has a significant impact on the Schottky barrier height, reverse leakage current, and barrier inhomogeneity of the devices.