Remote Epitaxial Growth of GaN Thin Films on Graphene Buffer Layer on SiC Substrates using Metalorganic Vapor-Phase Epitaxy

High-quality inorganic thin films on flexible substrates are crucial for advancing the field of flexible devices such as wearable sensors, flexible displays, and electronic devices. Remote epitaxy on graphene-coated substrates has emerged as a promising methodology for creating these thin films, offering the potential for mass production of superior material platforms. However, the remote epitaxy of GaN thin films using the widely favored metalorganic vapor-phase epitaxy (MOVPE) has been challenging, mainly due to the degradation of the graphene by the harsh MOVPE growth environment and poor nucleation of GaN on graphene.<br/>In this study, we demonstrate the successful remote epitaxial growth of GaN thin films on graphene buffer layer (GBL) on SiC substrates using MOVPE. The unique properties of GBL, including its strong adhesion to the SiC substrate and the quasi-2D surface that allows for epilayer release, make it a suitable candidate for enduring the harsh growth conditions of MOVPE and remote epitaxy. Moreover, the step edges of GBL, naturally formed by the SiC substrate during the graphitization process, provide numerous nucleation sites for GaN.<br/>To identify the optimum conditions for GaN film growth on GBL, we investigated the nucleation and lateral growth of GaN, with an emphasis on varying growth parameters such as temperature, pressure, and precursor flow rates. Notably, we found that the step edges of GBL served as effective nucleation sites for GaN. The resultant films exhibited smooth surface morphology, and their high crystalline quality was confirmed through XRD and EBSD analyses. Additionally, we successfully exfoliated and transferred these films onto different substrates, fully preserving their properties.<br/>This study opens new horizons for the large-scale production of high-quality, freestanding GaN membranes by overcoming previous challenges related to the remote epitaxy of GaN in the harsh MOVPE environment.