The mechanism of indium-assisted growth of (In)GaN nanorods: eliminating nanorod coalescence by indium-enhanced atomic migration

Abstract

Both well vertically aligned and uniformly separated (In)GaN nanorods (NRs) were successfully grown on Si(111) substrates by plasma-assisted molecular beam epitaxy. Effects of supplied indium (In) flux on the morphology of (In)GaN NRs were investigated systematically. The scanning electron microscopic analysis and transmission electron microscopic measurements revealed that the presence of In flux can help to inhibit NR coalescence and obtain well-separated (In)GaN NRs. By increasing the supplied In flux, the densities of (In)GaN NRs decreased and the axial growth rates increased. According to the energy dispersive X-ray spectrometry measurements and theoretical calculations, the increase of In content of the NRs enhanced Ga diffusion on the NR sidewalls, which resulted in an increased axial growth rate. A kinetic In-assisted growth model for the well-separated (In)GaN NRs is therefore proposed. The model explains that the presence of In flux not only reduces the density of (In)GaN NRs due to the increase in substrate surface migration of Ga adatoms at nucleation stage but also lead to a remarkable enhancement of axial growth rate at growth stage. Consequently, the NR coalescence was significantly suppressed. The results provide a demonstration of obtaining well-separated (In)GaN NRs and open up further possibility of developing (In)GaN NR-based optoelectronic devices.

Self-Integrated Hybrid Ultraviolet Photodetectors Based on the Vertically Aligned InGaN Nanorod Array Assembly on Graphene

“…Then, the cross-section HRTEM image, illustrated in Figure b, reveals that the region of TLG with a thickness of ∼1.2 nm can be identified underneath InGaN NR, where the carbon atomic columns are defined on account of the atoms located on the same horizontal dash line . The out-of-plane epitaxial relationship of InGaN(0001)//Si(111) can be determined according to the crystal lattice . In addition, selected area electron diffraction (SAED) and X-ray diffraction (XRD) 2θ–ω scan curves are further adopted to illustrate the structural information and overall directional alignment for InGaN NRAs on the graphene-on-Si substrate of InGaN(0001)//Si(111) and InGaN(101̅0)//Si(21̅1̅), , Figures S7a and S8, respectively, which are consistent with the HRTEM image and the simulated atom structure constructed by the DFT framework, Figure c.…”

Anisotropic Piezoelectric Response from InGaN Nanowires with Spatially Modulated Composition and Topography over a Textured Si(100) Substrate

“…The NW shapes are also clearly contoured by the Ga atom spatial distribution, with the GaN NWs on facet-2, exhibiting a tapered outline with a narrow top indicating the suppressed radial growth because of the lack of In atom incorporation. A uniform cylindrical shape with a flat top is observed on facet-4, which agrees well with the reported greater radial growth for InGaN NWs . TEM–EDX quantitative analysis with better spatial resolution is also presented in Figure S3.…”

Modulating Surface/Interface Structure of Emerging InGaN Nanowires for Efficient Photoelectrochemical Water Splitting

“…[69][70][71] In our previous work, it was found that increasing In flux would reduce the adsorption energy of Ga atoms on the sidewalls of NWs and thus enhance Ga migration rate, resulting in an increase in the axial growth rate. [72] Meanwhile, under In-rich conditions, the substrate surface migration of Ga atoms will be accelerated in the nucleation stage, which leads to the reduced density and suppressed merger of InGaN NWs. We also systematically studied the influence of Ga flux on the morphology, structure and optical properties of InGaN NWs.…”