Stress relaxation of GaN microstructures on a graphene-buffered Al2O3 substrate

• Published in: Physica status solidi. PSS-RRL. Rapid research letters 2014-04, Vol.8 (4), p.341-344
• Main Authors: Mun, Dae-Hwa, Bae, Hyojung, Bae, Sukang, Lee, Hyunjung, Ha, Jun-Seok, Lee, Sanghyun
• Format: Article
• Language: English
• Subjects: Chemical vapor deposition; Crystal lattices; epitaxial lateral overgrowth; GaN; Grain growth; graphene; Microstructure; Raman spectroscopy; residual stress; Spectrum analysis
• ISSN: 1862-6254; 1862-6270
• DOI: 10.1002/pssr.201400001

GaN microstructures were grown on c‐Al2O3 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‐Al2O3. Residual stress in the GaN microstructures was estimated from the peak shift of the E2 phonon using micro‐Raman spectroscopy. The results showed that the compressive stress of approximately 0.36 GPa in GaN on c‐Al2O3 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) In this Letter, the effect of graphene as a buffer layer on the growth and properties of GaN microstructures is investigated by the comparison with GaN grown on bare c‐Al2O3 under the same growth conditions. It is demonstrated that graphene significantly influences the nucleation as well as the relaxation of residual stress of GaN microstructures.