Microstructural and spectroscopic analysis of epitaxial lateral overgrowth GaN via the self-decomposing hexagonal graphene mask

The use of two-dimensional material like graphene to alleviate lattice mismatch has been an effective way to realize high-quality GaN on heterogeneous substrates. The lack of hanging bonds on the graphene surface provides a new attempt for epitaxial lateral overgrowth (ELOG). In this study, a hexagonal graphene mask was used for the growth of GaN, the graphene mask disappeared during the GaN growth process, but GaN still maintained the ELOG mode, and the threading dislocation density was significantly reduced. Raman and PL spectra demonstrated the stress relaxation in ELOG GaN and showed a stress relaxation of 0.157 GPa at the interface between the substrate and ELOG GaN. This study demonstrates the feasibility and advantages of graphene masks for nitrides and extends the research on stress relaxation of ELOG GaN using a graphene mask.