Impact of graphene state on the orientation of III–nitride

Abstract

We attempted to grow (10–13) semi-polar GaN on graphene to confirm the possibility of a remote epitaxy of semi-polar GaN. Single crystalline (10–13) GaN was obtained on an optimized template using optimized growth conditions. However, (10–13), (0002), and other GaN orientations were found under the same growth conditions on a graphene-coated template. Scanning transmission electron microscopy and energy-dispersive x-ray spectroscopy revealed that multi-domain GaN and (0002) GaN occurred in areas with a damaged graphene interfacial layer and intact graphene, respectively. Raman spectroscopy confirmed that graphene could survive under the growth conditions used here. Using cross-sectional scanning electron microscopy, we propose a simple approach to distinguish damaged graphene. Although the remote epitaxy of semi-polar GaN has not been demonstrated despite the usage of an optimized template and growth conditions, our results confirm the importance of the interfacial state in determining the crystallinity of the overgrown layer.

Remote Epitaxy: Fundamentals, Challenges, and Opportunities

“…Nevertheless, the validity of remote epitaxy has often been studied using wet transfer of graphene. 20,34 Although the interfacial contamination can be mitigated by employing dry transfer processes, 17 graphene inevitably forms wrinkles and tearing regardless of the transfer processes used, which deteriorates epilayer quality. 4,6 Therefore, it is clear that direct growth of 2D materials is the ideal approach to form pristine interfaces without contamination or substrate oxidation.…”

“…This shows the importance of graphene formation method and epitaxy conditions for successful remote epitaxy. 34 qvdW epitaxy, wherein the nucleation is driven by the vdW interaction between adatoms and 2D materials. The substrate underneath the 2D materials plays little or no role in the growth.…”

“…If wet-transferred graphene is employed to form epitaxy templates, it is difficult to keep the graphene/substrate interfaces free of contamination, because liquid trapped at the interface can form residue or induce substrate oxidation during the drying process. , Interfacial contamination increases the distance between the graphene and the substrate, and thus also the distance between the topmost atoms of the substrate and the bottommost atoms of epilayers, which is confirmed by cross-sectional transmission electron microscopy (TEM) measurements. , This will severely weaken the remote interaction and could even lead to the failure of remote epitaxy, as in the example shown in Figure c. Interfacial contamination could also induce a poor epilayer quality, in-plane rotation of nuclei or polycrystalline growth. , When oxidation of the substrates is severe, 2D materials can even be torn under epitaxy environment due to destructive deoxidation processes, which can induce nucleation from the damaged 2D area (Figure d). , These reports substantiate that utilizing wet-transferred graphene is prone to failure of remote epitaxy and thus should be avoided if possible. Nevertheless, the validity of remote epitaxy has often been studied using wet transfer of graphene. , Although the interfacial contamination can be mitigated by employing dry transfer processes, graphene inevitably forms wrinkles and tearing regardless of the transfer processes used, which deteriorates epilayer quality. , Therefore, it is clear that direct growth of 2D materials is the ideal approach to form pristine interfaces without contamination or substrate oxidation.…”

“…This shows the importance of graphene formation method and epitaxy conditions for successful remote epitaxy . Adapted with permission from ref . Copyright 2023 AIP Publishing.…”

“…Interfacial contamination could also induce a poor epilayer quality, 6 inplane rotation of nuclei 20 or polycrystalline growth. 17,34 When oxidation of the substrates is severe, 2D materials can even be torn under epitaxy environment due to destructive deoxidation processes, which can induce nucleation from the damaged 2D area (Figure 3d). 8,9 These reports substantiate that utilizing wet-transferred graphene is prone to failure of remote epitaxy and thus should be avoided if possible.…”