Stress relaxation of GaN microstructures on a graphene‐buffered Al 2 O 3 substrate

GaN microstructures were grown on c‐Al 2 O 3 with a multi‐stacked graphene buffered layer using metal metal‐organic chemical‐vapor deposition. Under the same growth conditions, the nucleation of GaN was suppressed by the low surface energy of graphene, resulting in a much lower density of microstructures relative to those grown on c‐Al 2 O 3 . Residual stress in the GaN microstructures was estimated from the peak shift of the E 2 phonon using micro‐Raman spectroscopy. The results showed that the compressive stress of approximately 0.36 GPa in GaN on c‐Al 2 O 3 caused by lattice mismatch and the difference in the thermal expansion coefficient was relaxed by introducing the graphene layer. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)