Quasi-free standing GaN epitaxial layer grown on nano-columnar GaN by RF-plasma assisted molecular beam epitaxy

A new approach for the growth of free standing GaN on sapphire substrates is demonstrated. The self-organized GaN nano-column structure is introduced as a buffer layer of overgrown GaN, which produces the air-bridge-like structure and brings about the relaxed residual strain in the overgrown GaN layers. X-ray investigation reveals that the quasi-free standing 2-3 mum thick Si-doped GaN layers are grown on sapphire substrates by rf-plasma assisted molecular beam epitaxy without the post-growth process and/or the regrowth procedure. Overgrown GaN peeled from GaN nano-column is observed due to a simple mechanical process.