Microstructural and optical properties of GaN buffer layers grown on graphene

A conventional two-step growth process is still the state-of-the-art technology for the epitaxy of GaN, even if graphene is used as a substrate. Low-temperature buffer layers play a decisive role in forming a continuous film. In this work, the informative characterization of low-temperature (550 °C) GaN buffer layers grown on graphene by hydride vapor phase epitaxy (HVPE) was performed. High-density and sixfold-symmetry structures of GaN nucleation sites formed the primary morphology of buffer layers. The E 2 (high) Raman shift of GaN buffer layers on graphene was 568 cm −1 , illustrating that GaN was free of stress. We also captured nonfocusing photoluminescence (PL) spectra and observed the high intensity of near-band-edge emission of wurtzite GaN and the absence of yellow luminescence in the visible band. Thermally induced quantum effects could be found in low-temperature PL. The elementary and detailed characterizations offer referenced values for the growth of GaN films on graphene.