Lead Catalyzed GaAs Nanowires Grown by Molecular Beam Epitaxy.

This study investigates the growth of gallium arsenide nanowires, using lead as a catalyst. Typically, nanowires are grown through the vapor-solid-liquid mechanism, where a key factor is the reduction in the nucleation barrier beneath the catalyst droplet. Arsenic exhibits limited solubility in conventional catalysts; however, this research explores an alternative scenario in which lead serves as a solvent for arsenic, while gallium and lead are immiscible liquids.

Instantaneous growth of single monolayers as the origin of spontaneous core-shell InGaN nanowires with bright red photoluminescence.

Increasing the InN content in the InGaN compound is paramount for optoelectronic applications. It has been demonstrated in homogeneous nanowires or deliberately grown nanowire heterostructures. Here, we present spontaneous core-shell InGaN nanowires grown by molecular beam epitaxy on Si substrates at 625 °C.

Model of a GaAs Quantum Dot in a Direct Band Gap AlGaAs Wurtzite Nanowire.

We present a study with a numerical model based on k→·p→, including electromechanical fields, to evaluate the electromechanical and optoelectronic properties of single GaAs quantum dots embedded in direct band gap AlGaAs nanowires. The geometry and the dimensions of the quantum dots, in particular the thickness, are obtained from experimental data measured by our group. We also present a comparison between the experimental and numerically calculated spectra to support the validity of our model.

Photoluminescence Redistribution of InGaN Nanowires Induced by Plasmonic Silver Nanoparticles.

Hybrid nanostructures based on InGaN nanowires with decorated plasmonic silver nanoparticles are investigated in the present study. It is shown that plasmonic nanoparticles induce the redistribution of room temperature photoluminescence between short-wavelength and long-wavelength peaks of InGaN nanowires. It is defined that short-wavelength maxima decreased by 20%, whereas the long-wavelength maxima increased by 19%.

Direct Band Gap AlGaAs Wurtzite Nanowires.

Wurtzite AlGaAs is a technologically promising yet unexplored material. Here we study it both experimentally and numerically. We develop a complete numerical model based on an 8-band method, including electromechanical fields, and calculate the optoelectronic properties of wurtzite AlGaAs nanowires with different Al content.

Self-assembled photonic structure: a Ga optical antenna on GaP nanowires.

Semiconductor nanowires are the perfect platform for nanophotonic applications owing to their resonant, waveguiding optical properties and technological capabilities providing control over their crystalline and chemical compositions. The vapor-liquid-solid growth mechanism allows the formation of hybrid metal-dielectric nanostructures promoting sub-wavelength light manipulation. In this work, we explore both experimentally and numerically the plasmonic effects promoted by a gallium (Ga) nanoparticle optical antenna decorating the facet of gallium phosphide (GaP) nanowires.

Selective Area Epitaxy of GaN Nanowires on Si Substrates Using Microsphere Lithography: Experiment and Theory.

GaN nanowires were grown using selective area plasma-assisted molecular beam epitaxy on SiO/Si(111) substrates patterned with microsphere lithography. For the first time, the temperature-Ga/N flux ratio map was established for selective area epitaxy of GaN nanowires. It is shown that the growth selectivity for GaN nanowires without any parasitic growth on a silica mask can be obtained in a relatively narrow range of substrate temperatures and Ga/N flux ratios.

Light-Emitting Diodes Based on InGaN/GaN Nanowires on Microsphere-Lithography-Patterned Si Substrates.

The direct integration of epitaxial III-V and III-N heterostructures on Si substrates is a promising platform for the development of optoelectronic devices. Nanowires, due to their unique geometry, allow for the direct synthesis of semiconductor light-emitting diodes (LED) on crystalline lattice-mismatched Si wafers. Here, we present molecular beam epitaxy of regular arrays n-GaN/i-InGaN/p-GaN heterostructured nanowires and tripods on Si/SiO substrates prepatterned with the use of cost-effective and rapid microsphere optical lithography.

Anisotropic Radiation in Heterostructured "Emitter in a Cavity" Nanowire.

Tailorable synthesis of axially heterostructured epitaxial nanowires (NWs) with a proper choice of materials allows for the fabrication of novel photonic devices, such as a nanoemitter in the resonant cavity. An example of the structure is a GaP nanowire with ternary GaPAs insertions in the form of nano-sized discs studied in this work. With the use of the micro-photoluminescence technique and numerical calculations, we experimentally and theoretically study photoluminescence emission in individual heterostructured NWs.

Purcell Effect and Beaming of Emission in Hybrid AlGaAs Nanowires with GaAs Quantum Dots.

Control of directionality of emissions is an important task for the realization of novel nanophotonic devices based on nanowires. Most of the existing approaches providing high directionality of the light emitted from nanowires are based on the utilization of the tapered shape of nanowires, serving as nanoantenna coupling with the light waveguided in nanowire and the directional output beam. Here we report the beaming of the emitted light with wavelength near 800 nm by naturally formed core-shell AlGaAs NW with multiply GaAs quantum dots (QDs) diameter 30 nm and height 10 nm, while the diameter of NW 130 nm, what does not support efficient emission into waveguided modes, including the mode HE.

Red GaPAs/GaP Nanowire-Based Flexible Light-Emitting Diodes.

We demonstrate flexible red light-emitting diodes based on axial GaPAs/GaP heterostructured nanowires embedded in polydimethylsiloxane membranes with transparent electrodes involving single-walled carbon nanotubes. The GaPAs/GaP axial nanowire arrays were grown by molecular beam epitaxy, encapsulated into a polydimethylsiloxane film, and then released from the growth substrate. The fabricated free-standing membrane of light-emitting diodes with contacts of single-walled carbon nanotube films has the main electroluminescence line at 670 nm.

Tailoring Morphology and Vertical Yield of Self-Catalyzed GaP Nanowires on Template-Free Si Substrates.

Tailorable synthesis of III-V semiconductor heterostructures in nanowires (NWs) enables new approaches with respect to designing photonic and electronic devices at the nanoscale. We present a comprehensive study of highly controllable self-catalyzed growth of gallium phosphide (GaP) NWs on template-free silicon (111) substrates by molecular beam epitaxy. We report the approach to form the silicon oxide layer, which reproducibly provides a high yield of vertical GaP NWs and control over the NW surface density without a pre-patterned growth mask.

Effect of crystal structure on the Young's modulus of GaP nanowires.

Young's modulus of tapered mixed composition (zinc-blende with a high density of twins and wurtzite with a high density of stacking faults) gallium phosphide (GaP) nanowires (NWs) was investigated by atomic force microscopy. Experimental measurements were performed by obtaining bending profiles of as-grown inclined GaP NWs deformed by applying a constant force to a series of NW surface locations at various distances from the NW/substrate interface. Numerical modeling of experimental data on bending profiles was done by applying Euler-Bernoulli beam theory.

Multi-colour light emission from InGaN nanowires monolithically grown on Si substrate by MBE.

InGaN nanostructures are among the most promising candidates for visible solid-state lighting and renewable energy sources. To date, there is still a lack of information about the influence of the growth conditions on the physical properties of these nanostructures. Here, we extend the study of InGaN nanowires growth directly on Si substrates by plasma-assisted molecular beam epitaxy.

Influence of TOPO and TOPO-CdSe/ZnS Quantum Dots on Luminescence Photodynamics of InP/InAsP/InPHeterostructure Nanowires.

The passivation influence by ligands coverage with trioctylphosphine oxide (TOPO) and TOPO including colloidal CdSe/ZnS quantum dots (QDs) on optical properties of the semiconductor heterostructure, namely an array of InP nanowires (NWs) with InAsP nanoinsertion grown by Au-assisted molecular beam epitaxy on Si (111) substrates, was investigated. A significant dependence of the photoluminescence (PL) dynamics of the InAsP insertions on the ligand type was shown, which was associated with the changes in the excitation translation channels in the heterostructure. This change was caused by a different interaction of the ligand shells with the surface of InP NWs, which led to the formation of different interfacial low-energy states at the NW-ligand boundary, such as surface-localized antibonding orbitals and hybridized states that were energetically close to the radiating state and participate in the transfer of excitation.

Structural and Optical Properties of Self-Catalyzed Axially Heterostructured GaPN/GaP Nanowires Embedded into a Flexible Silicone Membrane.

Controlled growth of heterostructured nanowires and mechanisms of their formation have been actively studied during the last decades due to perspectives of their implementation. Here, we report on the self-catalyzed growth of axially heterostructured GaPN/GaP nanowires on Si(111) by plasma-assisted molecular beam epitaxy. Nanowire composition and structural properties were examined by means of Raman microspectroscopy and transmission electron microscopy.

Fabrication and electrical study of large area free-standing membrane with embedded GaP NWs for flexible devices.

Flexible optoelectronic structures are required in a wide range of applications. Large scale modified silicone-embedded n-GaP nanowire arrays of a record 6 µm thin membranes were studied. A homogeneous silicone encapsulation was enabled by G-coating using a heavy-load centrifuge.

Effect of the Uniaxial Compression on the GaAs Nanowire Solar Cell.

Research regarding ways to increase solar cell efficiency is in high demand. Mechanical deformation of a nanowire (NW) solar cell can improve its efficiency. Here, the effect of uniaxial compression on GaAs nanowire solar cells was studied via conductive atomic force microscopy (C-AFM) supported by numerical simulation.

Ascending Si diffusion into growing GaN nanowires from the SiC/Si substrate: up to the solubility limit and beyond.

We report a novel mechanism that allows the incorporation of Si into GaN nanowires up to and beyond the solubility limit. This mechanism is documented during the growth on vicinal (misoriented) SiC/Si hybrid substrates having the step bunches. Nanowires that are grown at these locations become heavily Si doped.

Hydrogen passivation of the n-GaN nanowire/p-Si heterointerface.

The influence of hydrogen plasma treatment on the electrical and optical properties of vertical GaN nanowire (NW)/Si heterostructures synthesized via plasma assisted molecular beam epitaxy is studied. The effect of the treatment is thoroughly studied via variation of the passivation duration. Photoluminescence investigation demonstrates that the passivation affects the doping of the GaN NWs.

Wurtzite AlGaAs Nanowires.

Semiconducting nanowires, unlike bulk, can be grown in both wurtzite and zincblende crystal phases. This unique feature allows for growth and investigation of technologically important and previously unexplored materials, such as wurtzite AlGaAs. Here we grow a series of wurtzite AlGaAs nanowires with Al content varying from 0.

Effects of the surface preparation and buffer layer on the morphology, electronic and optical properties of the GaN nanowires on Si.

The role of Si (111) substrate surface preparation and buffer layer composition in the growth, electronic and optical properties of the GaN nanowires (NWs) synthesized via plasma-assisted molecular beam epitaxy is studied. A comparison study of GaN NWs growth on the bare Si (111) substrate, silicon nitride interlayer, predeposited AlN and GaO buffer layers, monolayer thick Ga wetting layer and GaN seeding layer prepared by the droplet epitaxy is performed. It is demonstrated that the homogeneity and the morphology of the NW arrays drastically depend on the chosen buffer layer and surface preparation technique.

Control of Conductivity of InGaAs Nanowires by Applied Tension and Surface States.

The electronic properties of semiconductor AIIIBV nanowires (NWs) due to their high surface/volume ratio can be effectively controlled by NW strain and surface electronic states. We study the effect of applied tension on the conductivity of wurtzite InGaAs ( ∼ 0.8) NWs.

Nanowire Quantum Dots Tuned to Atomic Resonances.

Quantum dots tuned to atomic resonances represent an emerging field of hybrid quantum systems where the advantages of quantum dots and natural atoms can be combined. Embedding quantum dots in nanowires boosts these systems with a set of powerful possibilities, such as precise positioning of the emitters, excellent photon extraction efficiency and direct electrical contacting of quantum dots. Notably, nanowire structures can be grown on silicon substrates, allowing for a straightforward integration with silicon-based photonic devices.

Anapoles in Free-Standing III-V Nanodisks Enhancing Second-Harmonic Generation.

Nonradiating electromagnetic configurations in nanostructures open new horizons for applications due to two essential features: a lack of energy losses and invisibility to the propagating electromagnetic field. Such radiationless configurations form a basis for new types of nanophotonic devices, in which a strong electromagnetic field confinement can be achieved together with lossless interactions between nearby components. In our work, we present a new design of free-standing disk nanoantennas with nonradiating current distributions for the optical near-infrared range.