One of the key challenges in integrating III-N optoelectronics based on one-dimensional nanostructures with CMOS technology on Si(100) is their inclined growth. Here, we first demonstrate that a nanostructured porous silicon layer on Si(100) enables precise control over GaN nanowire orientation, overcoming this fundamental issue. GaN nanowires grown from pores with height similar to 23-49 nm and diameter similar to 35-92 nm are predominantly normal to the substrate. X-ray diffraction reciprocal space mapping and reflection high-energy electron diffraction confirms the preferential vertical orientation of the nanowires. A thermodynamic model qualitatively explains the control mechanism: symmetric contact of a nascent GaN island with the pore's {111} sidewalls and (100) bottom yields normal orientation; asymmetry causes tilting. Optical studies reveal high structural quality of the nanowires: room-temperature photoluminescence exhibits an intense wurtzite GaN band at similar to 364 nm (FWHM similar to 9.4 nm), over threefold brighter than on bare Si(100). Raman spectroscopy shows an E-2(high) linewidth as narrow as similar to 2.7 cm(-1). This approach provides a promising CMOS-compatible pathway for integrating vertical GaN nanowire arrays on Si(100) substrate.

Precise spatial and morphological control in the synthesis of semiconductor nanostructures remains a critical challenge for the bottom-up fabrication of integrated nanosystems. Here, we demonstrate that the substrate topography can be used to deterministically control the van der Waals epitaxy of AlN nanostructures on hexagonal boron nitride (h-BN) flakes. Atomic force and scanning electron microscopy studies reveal that vertical AlN nanowires grow randomly on the h-BN surface, while nanowalls preferentially nucleate and propagate along the step edges of h-BN flakes. This morphological selectivity is governed by a critical step height: nucleation of nanowalls occurs only at the steps exceeding a height of 5 +/- 1 monolayers of h-BN. In the temperature range from 810 to 850 degrees C, increasing the growth temperature reduces the nanowire surface density and simultaneously enhances vertical growth of both nanowires and nanowalls. These trends are discussed within a qualitative model. This work establishes a new principle for topographical control over vdW epitaxy, opening a pathway for the fabrication of integrated deep-ultraviolet photonic circuits and ordered piezoelectric nanosystems.

This work is devoted to studying the features of the optical properties of self-catalyzed axially heterostructured GaNP/GaP nanowires on Si(111) grown by plasma-assisted molecular beam epitaxy. Transparent polydimethylsiloxane rubber was used to determine the photoluminescent properties of the grown NW arrays and the parasitic layer separately. Low-temperature photoluminescence studies demonstrate the transition to a quasi-direct bandgap in nanowires, which is characteristic feature of diluted nitrides with a low nitrogen content. The bright photoluminescent response at room temperature demonstrates the potential application of nanowires/rubber membranes in flexible optoelectronic devices. #COMESYSO1120.

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. Liquid lead easily dissolves in Si as well as in GaAs. The preservation of the catalyst during the growth process is also addressed. GaAs nanowires have been grown by molecular beam epitaxy on silicon Si (111) substrates at varying temperatures. Observations indicate the spontaneous doping of the GaAs nanowires with both lead and silicon. These findings contribute to a deeper understanding of the VLS mechanism involved in nanowire growth. They are also an important step in the study of GaAs nanowire-doping processes.

Zinc oxide (ZnO) nanostructures are widely used in various fields of science and technology due to their properties and ease of fabrication. To achieve the desired characteristics for subsequent device application, it is necessary to develop growth methods allowing for control over the nanostructures’ morphology and crystallinity governing their optical and electronic properties. In this work, we grow ZnO nanostructures via hydrothermal synthesis using surfactants that significantly affect the growth kinetics. Nanostructures with geometry from nanowires to hexapods are obtained and studied with photoluminescence (PL) spectroscopy. Analysis of the photoluminescence spectra demonstrates pronounced exciton on a neutral donor UV emission in all of the samples. Changing the growth medium chemical composition affects the emission characteristics sufficiently. Apart the UV emission, nanostructures synthesized without the surfactants demonstrate deep-level emission in the visible range with a peak near 620 nm. Structures synthesized with the use of sodium citrate exhibit emission peak near 520 nm, and those with polyethylenimine do not exhibit the deep-level emission. Thus, we demonstrate the correlation between the hydrothermal growth conditions and the obtained ZnO nanostructures’ optical properties, opening up new possibilities for their precise control and application in nanophotonics, UV–Vis and white light sources.

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.

In this work non-scanning far-field nonlinear optical microscopy is employed to study the whispering gallery modes in tapered GaN microwire resonators. We demonstrate the confinement of whispering gallery modes under near-infrared excitation with the photon energy close to half of GaN bandgap. Our results indicate the enhancement of yellow-green luminescence by whispering gallery modes in GaN microwires.

Engineering nonlinear optical responses at the microscale is a key topic in photonics for achieving efficient frequency conversion and light manipulation. Gallium nitride (GaN) is a promising semiconductor material for integrated nonlinear photonic structures. In this work, we use epitaxially grown GaN microwires as nonlinear optical whispering gallery and Fabry-Perot resonators. We demonstrate an effective generation of second-harmonic and polarization-dependent signals of whispering gallery and Fabry-Perot modes (FPM) under near-infrared (NIR) excitation. We show how the rotation of the excitation polarization can be used to control and switch between Fabry-Perot and whispering gallery modes in tapered GaN microwire resonators. We demonstrate the enhancement of two-photon luminescence in the yellow-green spectral range due to efficient coupling between whispering gallery, FPM, and excitonic states in GaN. This luminescence enhancement allows us to conveniently visualize whispering gallery modes excited with a NIR source. Such microwire resonators can be used as compact microlasers or sensing elements in photonic sensors.

Recently, III-V semiconductor nanostructures of reduced dimension attract more and more interest of researchers for the new generation devices creation. Combinations of nanostructures with different dimensions are of special interest, among them, for example, quantum dots in the body of nanowires. Such quantum dotsʼ size and location control is strictly determined by the growth parameters. As a result of effective relaxation of mechanical stresses on the lateral faces of nanowires, the integration of hybrid nanostructures with silicon technology is possible. In this work, we have demonstrated the possibility of GaP nanowires with GaAs quantum dots and AlGaP nanowires with InGaP quantum dots growth on silicon by molecular-beam epitaxy. The physical properties of the selected nanowires have been investigated. Growth experiments were performed using Riber Compact 21 setup, which is equipped, in addition to the growth chamber, with a vacuum-aligned chamber for gold deposition (metallization chamber). The morphological properties of the obtained nanostructures were studied by scanning electron microscopy. The optical properties of the nanostructures were investigated by the photoluminescence method. The analyses of morphological properties showed that GaP nanowires with GaAs quantum dots were formed predominantly in the <111> direction, in contrast to AlGaP nanowires with InGaP quantum dots, which in some cases changed the growth direction. The reason for the change in the direction of growth of nanowires may be the participation of indium in the growth process. With a sufficient content of indium in the gold catalyst droplet, such mixed droplet can etch the facets at the top of the nanowires, thereby descending to the side of the nanowires and changing the direction of nanowires growth. The studies of the optical properties of the grown nanostructures showed that the photoluminescence signal from InGaP quantum dots in AlGaP nanowires is observed at a temperature of –263 °C with a peak maximum of around 550 nm. Thus, the synthesized nanostructures are promising for optoelectronic applications, in particular, for creating sources of single-photons.

The ability to engineer nonlinear optical emission from nanostructures is a key challenge to create efficient and compact components for integrated devices. This paper shows a method to control and manipulate the directionality of second‐harmonic generation emission by engineering geometry and position of rod nanoantennas. Single and dimer nanoantennas are fabricated by slicing III–V semiconductor nanowires with focused ion beam milling. The nonlinear optical response of nanoantennas is tailored by adjusting their length and position to achieve a targeted phase difference. The studied GaAs nanoantennas have a wurtzite structure that allows to achieve preferable directions for the second‐harmonic emission compared to a typical bulk zinc blende structure from top‐down fabricated nanostructures. Wurtzite nanoantennas provide a pure electric dipole response at the second‐harmonic wavelength, which together with pi‐phase control of emitted light is used for designing nonlinear emission patterns. The simulation results show how to redirect the second‐harmonic beam up to 30° and how to tailor the emission profile by adding elements. This method of second‐harmonic generation manipulation and phase array engineering can be applied to different types of nanowires and nanostructures. Nonlinear beam steering with structures from nanowires will foster the creation of compact optical components for integrated circuits.

Composition of ternary III-V nanowires became a subject of recent intensive studies inspired by several optoelectronic applications. Among these nanostructures, phosphide nanowires possess a wider bandgap making it especially promising for applications operating in the green visible range. However, unlike other III-V materials, the growth of AlGaP nanowires remains rather unexplored. In this work, we model the stationary composition of self-catalyzed AlGaP grown by molecular beam epitaxy. We show that under a wide range of growth parameters our theoretical approach does not require any fitting parameter and thus allows direct interpretation of experimental data. The obtained numerical results demonstrate a tendency to Al domination over Ga at rather low fluxes of the first. Interesting phenomena of the rise of Al fraction with an increase of the total group III flux is demonstrated. On the other hand, high tolerance of the chemical composition to the temperature, concentration of phosphorus in the droplet, and adatom kinetics is shown numerically.

Despite poor crystallinity, a dilute nitride phosphide heterostructure with 5% nitrogen content demonstrates PL response at RT centered at 1.76 eV.

The growth mechanisms of self-catalyzed InAs/InSb axial nanowire heterostructures are thoroughly investigated as a function of the In and Sb line pressures and growth time. Some interesting phenomena are observed and analyzed. In particular, the presence of In droplet on top of InSb segment is shown to be essential for forming axial heterostructures in the self-catalyzed vapor-liquid-solid mode. Axial versus radial growth rates of InSb segment are investigated under different growth conditions and described within a dedicated model containing no free parameters. It is shown that widening of InSb segment with respect to InAs stem is controlled by the vapor-solid growth on the nanowire sidewalls rather than by the droplet swelling. The In droplet can even shrink smaller than the nanowire facet under Sb-rich conditions. These results shed more light on the growth mechanisms of self-catalyzed heterostructures and give clear route for engineering the morphology of InAs/InSb axial nanowire heterostructures for different applications.

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. To study the optical properties of the synthesized nanoheterostructures, the nanowire array was embedded into the silicone rubber membrane and further released from the growth substrate. The reported approach allows us to study the nanowire optical properties avoiding the response from the parasitically grown island layer. Photoluminescence and Raman studies reveal different nitrogen content in nanowires and parasitic island layer. The effect is discussed in terms of the difference in vapor solid and vapor liquid solid growth mechanisms. Photoluminescence studies at low temperature (5K) demonstrate the transition to the quasi-direct gap in the nanowires typical for diluted nitrides with low N-content. The bright room temperature photoluminescent response demonstrates the potential application of nanowire/polymer matrix in flexible optoelectronic devices.

Out-of-plane Ga2Se3 nanowires are grown by molecular beam epitaxy via Au-assisted heterovalent exchange reaction on GaAs substrates in the absence of Ga deposition. It is shown that at a suitable temperature around 560 degrees C the Audecorated GaAs substrate releases Ga atoms, which react with the incoming Se and feed the nanowire growth. The nanowire composition, crystal structure, and morphology are characterized by Raman spectroscopy and electron microscopy. The growth mechanism is investigated by X-ray photoelectron spectroscopy. We explore the growth parameter window and find an interesting effect of shortening of the nanowires after a certain maximum length. The nanowire growth is described within a diffusion transport model, which explains the nonmonotonic behavior of the nanowire length versus the growth parameters. Nanowire shortening is explained by the blocking of Ga supply from the GaAs substrate by thick, in-plane worm-like Ga2Se3 structures, which grow concomitantly with the nanowires, followed by backward diffusion of Ga atoms from the nanowires down to the substrate surface.

We present an image-based autofocusing system applied in nonlinear microscopy and spectroscopy with a wide range of excitation wavelengths. The core of the developed autofocusing system consists of an adapted two-step procedure maximizing an image score with six different image scorings algorithms implemented to cover different types of focusing scenarios in automated regime for broad wavelength region. The developed approach is combined with an automated multi-axis alignment procedure. We demonstrate the key abilities of the autofocusing procedure on different types of structures: single nanoparticles, nanowires and complex 3D nanostructures. Based on these experiments, we determine the optimal autofocusing algorithms for different types of structures and applications.

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. In this work we show controlled growth of nanowire-quantum-dot structures on silicon, frequency tuned to atomic transitions. We grow GaAs quantum dots in AlGaAs nanowires with a nearly pure crystal structure and excellent optical properties. We precisely control the dimensions of quantum dots and their position inside nanowires and demonstrate that the emission wavelength can be engineered over the range of at least 30 nm around 765 nm. By applying an external magnetic field, we are able to fine-tune the emission frequency of our nanowire quantum dots to the D2 transition of 87Rb. We use the Rb transitions to precisely measure the actual spectral line width of the photons emitted from a nanowire quantum dot to be 9.4 ± 0.7 μeV, under nonresonant excitation. Our work brings highly desirable functionalities to quantum technologies, enabling, for instance, a realization of a quantum network, based on an arbitrary number of nanowire single-photon sources, all operating at the same frequency of an atomic transition.

In our work, we employ the resonant electromagnetic properties of III-V semiconductor nanowires to design building blocks for nonlinear all-dielectric metamaterials and devices. Contrary to widely used Si and Ge nanostructures, III-V materials, such as GaAs or AlGaAs, have a direct band gap and non-centrosymmetric crystal structure, which makes them promising for the development of nonlinear metamaterials. We developed an innovative approach to fabricate disk and rod nanoantennas by slicing bottom-up grown nanowires using a focused ion beam milling (FIB). The proposed method allows to significantly decrease the influence of the substrate on the electromagnetic field distribution inside the nanoantenna and it opens the possibility to use any substrate regardless of the nanostructure fabrication process. With this technique, we study the influence of geometry, design and crystal structure on the characteristics of all-dielectric nanoantennas. It offers unique opportunities to fabricate high-quality structures with variable radii, longitudinal heterostructures with lattice-mismatched materials, and structures with different refractive indexes and crystal phases that are not available in bulk materials.

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. We show a novel approach to creating nanoantennas by slicing III-V nanowires into standing disks using focused ion-beam milling. We experimentally demonstrate the suppression of the far-field radiation and the associated strong enhancement of the second-harmonic generation from the disk nanoantennas. With a theoretical analysis of the electromagnetic field distribution using multipole expansions in both spherical and Cartesian coordinates, we confirm that the demonstrated nonradiating configurations are anapoles. We expect that the presented procedure of designing and producing disk nanoantennas from nanowires becomes one of the standard approaches to fabricating controlled chains of standing nanodisks with different designs and configurations. These chains can be essential building blocks for new types of lasers and sensors with low power consumption.

In this paper we study growth of quasi-one-dimensional GaN nanowires (NWs) and nanotube (NT)-like nanostructures on Si(111) substrates covered with a thin AlN layer grown by means of plasma-assisted molecular beam epitaxy. In the first part of our study we investigate the influence of the growth parameters on the geometrical properties of the GaN NW arrays. First, we find that the annealing procedure carried out prior to deposition of the AlN buffer affects the elongation rate and the surface density of the wires. It has been experimentally demonstrated that the NW elongation rate and the surface density drastically depend on the substrate growth temperature, where 800 °C corresponds to the maximum elongation rate of the NWs. In the second part of the study, we introduce a new dopant-stimulated method for GaN nanotube-like nanostructure synthesis using a high-intensity Si flux. Transmission electron microscopy was used to investigate the morphological features of the GaN nanostructures. The synthesized structures have a hexagonal cross-section and possess high crystal quality. We propose a theoretical model of the novel nanostructure formation which includes the role of the dopant Si. Some of the Si-doped samples were studied with the photoluminescence (PL) technique. The analysis of the PL spectra shows that the highest value of donor concentration in the nanostructures exceeds 5∙1019 cm−3.