Molecular Beam Epitaxy of GaN Nanowires on Epitaxial Graphene (original) (raw)
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GaN‐Based Nanorods/Graphene Heterostructures for Optoelectronic Applications
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The insulating character of sapphire, meltback etching of Si, bulk and surface defects prevented the efficient integration of GaN nanostructures in optoelectronic devices. Here, it is demonstrated that graphene can simultaneously serve as an electrical bottom contact, a chemically inert buffer layer, and a superior lattice and thermal matched growth substrate. Vertically aligned, high crystal quality GaN nanorods (NRs) without bulk defects such as threading dislocations and with only a mild strain at the NRs’ base are grown by metal‐organic vapor‐phase epitaxy on defect‐free graphene using nanometer‐sized AlxGa1−xN nucleation islands. Here no influence of the supporting substrate on the GaN epitaxy is observed. However, at defects in graphene the effects of dangling bonds and the underlying substrate, presumably through nanoholes in graphene, on the properties of GaN NRs are visible. It is also shown that surface defects in InxGa1−xN/GaN NRs from planar films produced by etching of ...
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GaN Nanowires Grown by Molecular Beam Epitaxy
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The unique properties of GaN nanowires grown by molecular beam epitaxy are reviewed. These properties include the absence of residual strain, exclusion of most extended defects, long photoluminescence lifetime, low surface recombination velocity, and high mechanical quality factor. The high purity of the nanowires grown by this method allows for controllable ntype doping. P-type doping presents more challenges but has been demonstrated in active light-emitting diode devices. The present understanding of nucleation and growth of these materials is also reviewed.
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We present detailed Raman studies of graphene deposited on gallium nitride nanowires with different variations in height. Our results indicate that different density and height of nanowires impact graphene properties such as roughness, strain, and carrier concentration as well as density and type of induced defects. Tracing the manifestation of those interactions is important for the application of novel heterostructures. A detailed analysis of Raman spectra of graphene deposited on different nanowire substrates shows that bigger differences in nanowires height increase graphene strain, while a higher number of nanowires in contact with graphene locally reduces the strain. Moreover, the value of graphene carrier concentration is found to be correlated with the density of nanowires in contact with graphene. The lowest concentration of defects is observed for graphene deposited on nanowires with the lowest density. The contact between graphene and densely arranged nanowires leads to a...
Properties of GaN Nanowires Grown by Molecular Beam Epitaxy
IEEE Journal of Selected Topics in Quantum Electronics, 2000
The unique properties of GaN nanowires grown by molecular beam epitaxy are reviewed. These properties include the absence of residual strain, exclusion of most extended defects, long photoluminescence lifetime, low surface recombination velocity, and high mechanical quality factor. The high purity of the nanowires grown by this method allows for controllable ntype doping. P-type doping presents more challenges but has been demonstrated in active light-emitting diode devices. The present understanding of nucleation and growth of these materials is also reviewed.
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We report experiments on the formation of GaN nanowires on epitaxial GaN using thin layers of Ni. GaN covered with Ni shows roughening that is strongly dependent on the thickness of the Ni layer and the annealing conditions. With the initial Ni thickness of 0.8 nm we observe formation of Ni-filled antidots. These act as nucleation sites in the growth of GaN nanowires, allowing for the preparation of nanowires with an average diameter as small as 30 nm. Dense and well-oriented nanowires are formed by pulsed metallorganic chemical vapor deposition at 750°C. The size of the Ni features determines the diameter of the GaN nanowires, resulting in good control over the formation process.
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Applied Sciences
Single-layer (SLG)/few-layer (FLG) and multilayer graphene (MLG) (>15 layers) samples were obtained using the CVD method on high-textured Cu foil catalysts. In turn, plasma-assisted molecular beam epitaxy was applied to carry out the GaN graphene-assisted growth. A thin AlN layer was used at the initial stage to promote the nucleation process. The effect of graphene defectiveness and thickness on the quality of the GaN epilayers was studied. The bilayer graphene showed the lowest strain and provided optimal conditions for the growth of GaN/AlN. Theoretical studies based on the density functional theory have shown that the energy of interaction between graphene and AlN is almost the same as between graphite sheets (194 mJ/m2). However, the presence of vacancies and other defects as well as compression-induced ripples and nitrogen doping leads to a significant change in this energy.
Growth of GaN nanostructures on graphene
International Conference on Nanoscience, Engineering and Technology (ICONSET 2011), 2011
GaN nanostructures with different morphologies are grown on few layer graphene (FLG) as template, using chemical vapor-deposition technique in a self catalytic process using the large surface energy of graphene. Raman and photoluminescence studies reveal wurtzite GaN phase. Morphologies of these nanostructures varied depending on the number of layers in each template. Photoluminescence study reveals that growth occurs without deterioration of FLG layers and no incorporation of carbon in GaN nanostructures Keywords-gallium nitride; GaN; graphene; nanostructures; Raman spectroscopy; photoluminescence I.