Self-assembly graphene nanomask for epitaxial growth of nonplanar and planar GaN

Taking advantage of the unique properties of two-dimensional (2D) materials, van der Waals epitaxy or remote epitaxy of nonplanar and planar materials on 2D materials plays an important role in the application, but is often limited by low crystalline quality with misorientation in nonplanar materials, or grain boundaries and high threading dislocation densities in planar materials. Selective area growth (SAG) is an effective way to break the limitation, in which orientation is concordant, grain boundaries can be avoided, and threading dislocations can be annihilated. It is believed that microscale materials are predominant masks for SAG, and nanoselective area growth (NSAG) technology is more superior, which may allow epilayer mechanical exfoliation from substrate. Here we demonstrate fabrication of architectural GaN nanostructures by self-assembly NSAG (SNSAG) technology using multilayer graphene (MLG) as a nanomask. The microstructure and optical properties, measured by scanning electron microscopy, transmission electron microscopy, cathodeluminescence, micro-Raman, and micro-photoluminescence, were characterized for evidencing the high-quality GaN nanostructures. Moreover, high-quality, stress-relaxation GaN films were SNSAG on MLG/SiC and mechanically exfoliated from substrates for obtaining free-standing GaN. This technique enables integration of any nonplanar and planar semiconductor materials with graphene for the extensible application.