GaN‐Based Nanorods/Graphene Heterostructures for Optoelectronic Applications

Abstract

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 the defective material can be effectively passivated with only 10 nm alumina deposited by atomic layer deposition. This is confirmed by the increase in electroluminescence measured on finished devices with graphene top contact. These results can potentially lead to new material combinations including graphene, GaN, and other relevant semiconductors like Si toward yet unexplored device concepts.

Impact of kinetics on the growth of GaN on graphene by plasma-assisted molecular beam epitaxy

“…As previously noted, additional local energy minima are found from the preferred epitaxial relationship in XRD data shown in figure 8. Intermediate orientations were previously reported at 19° correlated to the existence of preferential Ga/N adsorption sites on the graphene surface at the midpoint between graphene atoms (B sites) [25,28]. Indeed, when the discreet calculation is repeated for exclusively B-sites (B-site sublattice) without considering the VdW gap, new minima are observed at  19⁰ and 41⁰ (figure 10).…”

Development and Applications of ReaxFF Reactive Force Fields for Group-III Gas-Phase Precursors and Surface Reactions with Graphene in Metal–Organic Chemical Vapor Deposition Synthesis

“…Graphene, a single layer of sp 2 carbon, is an attractive candidate as a substrate because of the van der Waals interactions with its environment and the hexagonal arrangement of atoms in graphene, which is similar to the (0001) c -plane of group-III nitrides. Furthermore, the thermal stability, high decomposition temperature, transferability, optical transparency, and electrical conductivity make graphene a promising substrate for group-III nitride nanowires − and thin films. − For instance, Al Balushi et al demonstrated that the chemical reactivity and the thickness of a graphene substrate impact the nucleation of group-III nitride layers, and nitrogen defects affect the nucleation and growth of GaN and AlN on graphene. Qi et al .…”

Correlative Microscopy and Spectroscopy Workflow for Microplastics

“…4,9,10 However, these correlative investigations require easy relocalization of the same objects in different instruments, which is becoming increasingly difficult with decreasing objects' size. [11][12][13][14] As an alternative, it has been shown for diverse types of materials that the same region of interest (ROI) can be precisely relocalized and measured in an hyphenated SEM-Raman system (also with EDS) in combination with a light microscope. [15][16][17] In this work, we demonstrate the first use of such a correlative microscopy and spectroscopy workflow on standard MP particles employing an optical zoom microscope and a combined SEM-Raman instrument.…”