Free standing GaN layers with GaN nanorod buffer layer

Thick GaN films were grown by HVPE (Hydride Vapor Phase Epitaxy) on c‐sapphire substrates with GaN nano‐rod buffer layers. Lateral epitaxial growth mode was adapted to grow GaN thick films on nano‐structure buffer. Thick GaN films were self‐separated during cooling down by thermal stress caused by the difference of thermal expansion coefficient (TEC) between GaN and sapphire. Since the nano‐rod buffer consists of nano‐rods and voids, it is mechanically weaker than planar GaN layers and contributes to the self‐separation of GaN thick films. 200 μm‐thick free‐standing GaN substrates show smooth surface morphology without any microcracks. The full width at half maximum (FWHM) of (0002) X‐ray rocking curve is 619 [arcsec]. Donor‐bound exciton emission is observed at 3.4718 eV in low‐temperature photoluminescence spectra, which is nearly the same peak position as bulk GaN. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)