Influence of polarities of GaN substrates on surface morphologies and physical properties of epitaxial Mg-doped GaN films grown by MOCVD

Herein, the influence of free-standing GaN (FS-GaN) substrates with different polarities on the surface morphologies and physical properties of epitaxial Mg-doped GaN films grown by metal-organic chemical vapor deposition (MOCVD) is investigated. For the Mg-doped GaN films grown on polar, semipolar, and nonpolar FS-GaN substrates, their surface morphologies vary greatly, which is attributed to the different surface states and growth modes. All films show high crystalline quality and are basically in a stress-free state. For polar p-GaN, good ohmic contact is achieved with Ni/Au electrode. For semipolar and nonpolar p-GaN, there are obvious contact barriers between the p-GaN and the metal electrodes, and the Mg-doping concentration may be higher than that of the c-plane epitaxial GaN according to the intensity ratio of the band edge peak with respect to the ultraviolet luminescence peak in photoluminescence spectra, which will be investigated in the near future. (© 2022 Wiley‐VCH GmbH)