Microstructure of porous gallium nitride nanowall networks

Porous GaN films consisting of irregular nanowall arrays were heteroepitaxially grown on 6H–SiC(0001) substrates by ion-beam-assisted molecular beam epitaxy at different substrate temperatures. X-ray diffraction, Rutherford backscattering spectrometry, scanning electron microscopy as well as scanning transmission electron microscopy (STEM) were applied to investigate the porous GaN thin films. Special attention was focused on the characterization of the microstructure of the thin films using a Cs-corrected high-resolution STEM. A high crystalline quality of the formed hexagonal GaN nanowalls was demonstrated. Based on the results, a growth mechanism of porous GaN thin films is discussed.