Multiple epitaxial lateral overgrowth of GaN thin films using a patterned graphene mask by metal organic chemical vapor deposition

Abstract

Single-crystal gallium nitride (GaN) thin films were grown using a graphene mask via multiple epitaxial lateral overgrowth (multiple-ELOG). During the growth process, the graphene mask self-decomposed to enable the emergence of a GaN film with a thickness of several hundred nanometres. This is in contrast to selective area growth of GaN using an SiO2 mask leading to the well known hexagonal-pyramid shape under the same growth conditions. The multiple-ELOG GaN had a single-crystalline wurtzite structure corresponding to the crystallinity of the GaN template, which was confirmed with electron backscatter diffraction measurements. An X-ray diffraction rocking curve of the asymmetric 102 reflection showed that the FWHM for the multiple-ELOG GaN decreased to 405 from 540′′ for the underlying GaN template. From these results, the self-decomposition of the graphene mask during ELOG was experimentally proven to be affected by the GaN decomposition rather than the high-temperature/H2 growth conditions.

Transferable Thru-Hole Epitaxy of GaN and ZnO, Respectively, Over Graphene and MoS2 as a 2D Space Layer

“…The experimental results could have been explained if the areal fraction of holes on graphene had increased during the growth. From a previous comparative study on the robustness of graphene transferred onto either GaN or sapphire, it was found that graphene transferred onto GaN was found to be damaged due to the thermal decomposition of GaN, while graphene transferred onto sapphire was found to be not damaged because there is no thermal decomposition of sapphire . Hence, the possibility of additional generation of holes on graphene during the growth can be excluded in our case.…”

MOVPE Growth of GaN via Graphene Layers on GaN/Sapphire Templates

“…While most of the graphene layer surface was smooth, some wrinkles and possible few-layer zones were observed ( Figure 1 a). Since direct epitaxy through defects, such as cracks and pinholes, followed by lateral overgrowth [ 22 , 23 ], might significantly aggravate the epilayer exfoliation, to avoid such a growth mode, stacks of two and three graphene monolayers (double-stack and triple-stack, hereinafter) were formed by repeating the complete transfer and cleaning procedures for each monolayer. In this approach, illustrated in Figure 1 b,c, overlapping stacks of the graphene monolayer cover the underlying defects, thus reducing the possibility of direct epitaxy.…”

“…The main disadvantages of dry transfer are the appearance of cracks, due to the interaction with hard surfaces, and a relatively high material cost [ 19 ]. Cracks in the graphene layer initiate growth through holes followed by lateral overgrowth [ 22 , 23 ]. Therefore, we used the relatively inexpensive wet transfer method to reduce the formation of cracks.…”

Large-Scale and High-Quality Iii-Nitride Membranes Through Microcavity-Assisted Crack Propagation by Engineering Tensile-Stressed Ni Layers

“…However, only partial and patterned III-nitride membranes have been demonstrated due to the lack of suitable ways to fully exfoliate the layers by overcoming the even reduced interfacial toughness [9,10]. In addition, although another promising separation technique has also recently been introduced by using two-dimensional (2D) materials such as graphene and boron nitrides as an intermediate layer [11,12], there are still many issues to be solved such as damages of the 2D materials according to the growth conditions, deterioration of the quality of the thin film due to defects from the 2D materials itself (e.g., tears, wrinkles, and residues), and screening of the lattice [13][14][15][16][17][18].…”