Fig 1

The properties of graphene(Gr)/sapphire substrate for epitaxial growth."

Fig 2

Characterizations of Gr/sapphire substrate. (a) Photographs of as-grown 2-inch Gr/sapphire substrate 44; (b) SEM image of the as-grown Gr films on flat sapphire substrates 44; (c) SEM image of the as-grown Gr films on nanopatterned sapphire substrate 35; (d) Raman spectra measured from representative positions in figure (a) 44; (e) G band Raman mapping of as-grown Gr film on sapphire 34; (f) Full-range XPS spectrum of the directly grown Gr on sapphire substrate 34; (g) The C 1s XPS spectrum of the directly grown Gr on sapphire substrate 34; (h) TEM image on the edge of the Gr film showing its monolayer feature 34; (i) Atomically resolved Z-contrast image of Gr 34. "

Fig 3

Tunable nucleation of AlN on Gr/sapphire substrate. (a) Schematic illustration of the nucleation of AlN on bare sapphire and Gr/sapphire 45; (b) SEM image of the nucleation of AlN on bare sapphire and pristine Gr-buffered sapphire 45; (c) Statistics of the density and size of the AlN nuclei on sapphire and pristine Gr/sapphire 45; (d) Raman spectra of Gr/sapphire substrate before N2 plasma treatment (black) and after N2 plasma treatment (red) 34; (e) C 1s XPS spectrum of N2-plasma-treated Gr/sapphire 34; (f) N 1s XPS spectrum of N2-plasma-treated Gr/sapphire 34; (g) DFT calculations of the bonding of one Al adatom on pyrrolic N in Gr 34; (h) AFM height image of AlN nucleation on plasma-treated Gr/sapphire substrate 34; (i) Density and size distribution analysis of AlN nucleation on bare sapphire and plasma-treated Gr/sapphire substrate 34. "

Fig 4

Fast epitaxial lateral overgrowth of AlN on Gr/sapphire substrate. (a) Schematic diagram of the fast growth of AlN film on N2-plasma-treated Gr/sapphire substrate 34; (b, c) SEM image of as-grown AlN on bare sapphire substrate and plasma-treated Gr/sapphire substrate with increasing growth time to 1 h, respectively 34; (d) AFM height image of as-grown AlN film on plasma-treated Gr/sapphire substrate 34; (e) SEM image of the initial 10 min growth of AlN on Gr/nano-patterned sapphire substrate 35; (f) and (g) show the cross-sectional SEM images of AlN films grown on nano-patterned sapphire and Gr/nano-patterned sapphire substrate, respectively 35. "

Fig 5

The stress relaxation of AlN film grown on Gr/sapphire substrate. (a) Schematics for the AlN/Gr/sapphire interface 45; (b, c) SAED patterns of the AlN/Gr/sapphire (b) and the AlN/sapphire (c) 45; (d) The E2(high) Raman frequency of AlN obtained on sapphire, horizontal Gr/sapphire, VG nanowall/sapphire, and bulk AlN substrates 46; (e) The corresponding biaxial stress for bulk AlN (657.4 cm-1) and AlN films on sapphire substrates with different types of Gr layers 46; (f) Optical microscopy images of the surface of the as-grown AlN film at the edge of the sapphire wafer with (top panel) and without (bottom panel) Gr 46. "

Fig 6

The reduced dislocation density of AlN epilayer grown on Gr/sapphire substrate 34. (a) X-ray rocking curves of (0002) AlN grown on sapphire (cyan line) and Gr/sapphire substrate (red line); (b) X-ray rocking curves of (10${\rm{\bar 1}}$2) AlN grown on sapphire (cyan line) and Gr/sapphire substrates (red line); (c) Grazing-incidence X-ray diffraction azimuthal off-axis phi scan for Al2O3 (113) and AlN (101); (d) Selected-area electron diffraction pattern taken at an AlN/Gr/sapphire interface."

Fig 7

The growth mode of AlN grown on Gr/sapphire substrate."

Fig 8

Enhanced heat dissipation of AlN film on vertical Gr/sapphire substrate 46. (a) AFM height image of vertical Gr/sapphire substrate; The inset shows a height profile of the AFM image with an average height ≈ 20 nm; (b) A representative cross-sectional TEM image of a vertical Gr nanosheet; (c) The cross-section TEM image of AlN/vertical Gr/sapphire, showing obvious VG nanowalls structures; (d) Schematic illustrations of an AlN/sapphire and an AlN/vertical Gr/sapphire structure; (e) Simulated 2D distributions of the heat mapping of an AlN/sapphire and an AlN/vertical Gr/sapphire structure cross-section; (f) The measured temperatures of AlN/sapphire and an AlN/vertical Gr/sapphire are plotted as a function of the time as detected by an infrared thermal imaging camera. The insets show the temperature distributions of AlN under laser irradiation for 5 min. "

Fig 9

Fabrication of high-brightness LED on Gr/sapphire substrate. (a) Schematic illustration of the as-fabricated blue LED structure 44; (b) Cross-sectional STEM image of InxGa1–xN/GaN MQWs in the as-fabricated blue LED 44; (c) Atomic-resolution STEM image of InxGa1–xN/GaN QW lattice 44; (d) Light-out power of the as-fabricated blue LED on Gr/sapphire and bare sapphire substrate 44; (e) Light output power of the UV-LED fabricated on vertical Gr/sapphire and bare sapphire substrate 46; (f) Light output power of the as-fabricated DUV-LED with and without Gr interlayer as a function of injection current 34. "

Fig 10

Fabrication and transfer processes for LED grown on graphene-layer substrates by utilizing graphene as transfer medium or transparent conductive electrode. (a) Schematic illustration of the fabrication and transfer processes for thin-film LED grown on Gr-layer substrates 14; (b) Optical images of light emissions from the as-fabricated LED on the original substrate and transferred LED on the foreign metal, glass, and platic substrates 14; (c) Optical microscope image from the p-GaN side of LED device (before flip-chip) on Gr/silica glass 69; (d) Schematic of the fabricated flip-chip UV LED device 69; (e) Electroluminescence spectrum measured for a 150 μm diameter aperture LED device under a bias of 20 V 69. "