Branched III-V nanowires (NWs) are interesting both from the fundamental viewpoint and for the development of electronic and optoelectronic structures with enhanced functionality. Herein, we present a robust approach to synthesis of branched AlGaAs NWs using the Au-catalyzed molecular-beam epitaxy directly on Si(111) substrates. The second and third deposition of Au onto the substrate with NWs gives rise to the first and second generation of branches. First generation branches grow in the [1-100] direction perpendicular to the NW trunks; their coalescence yields the NW bridging. Compositional and structural analysis, performed by transmission electron microscopy and Raman spectroscopy, reveal an AlAs fraction of 0.2-0.3 and almost pure wurtzite crystal phase of both NW trunks and uncoalesced branches of the first generation. According to the microscopy measurements the wurzite phase purity is more than 95%. The method is useful for obtaining complex branched structures in wurtzite AlGaAs NWs on Si substrates, and may be translated to other material systems. These branched structures open new perspectives for next generation optoelectronic, energy harvesting and biological devices.

A significant (up to 4 times) photoluminescence enhancement of single InP/InAsP/InP nanowires transferred onto a silicon oxide-covered silver layer on silicon substrate with a metal surface roughness level of less than 1 nm and a dielectric thickness of 5 nm has been demonstrated. This phenomenon is explained by the interaction of electron-hole pairs in the semiconductor with surface plasmon polaritons. The photoluminescence kinetics and results of modeling confirm the indicated enhancement mechanism.

The photoluminescence of nanostructures in the form InP/InAsP/InP nanowires, passivated by layers of colloidal $\mathrm{CdSe} / \mathrm{ZnS}$ quantum dots at increasing pump power, has been studied. A feature of the system is the existence of several luminescent centers connected through mechanisms of multi-stage non-radiative excitation transfer. It has been shown that the kinetics of decay of excited states depends on the nature of excitation. The effects of ‘filling exciton states” and “delayed confinement effect” are discussed

InGaAs quantum dots in AlGaAs nanowires were formed using molecular-beam epitaxy on the silicon surface for the first time. The dependence of the synthesized nanostructures physical properties on growth conditions was studied. The results of optical properties studies showed that photoluminescence spectra from InGaAs quantum dots are observed at room temperature in a wide range of wavelengths from 850 to 1300 nm. Based on experimental data, modeling of the optical properties of the synthesized nanostructures was carried out.

It has been revealed that removing the shell of spontaneously formed InGaN nanowires increases the amplitude and narrows their emission spectrum. It has been established that radiative recombination dominates in the nanowires. And the dependence of the integrated photoluminescence intensity on the pump power for nanowires after etching is superlinear in comparison with the initial ones.

We study the influence of the shell in InGaN nanowires with spontaneously formed core-shell structure on their optical and morphological properties. It is shown that removing the shell from the initial nanowires induces the photoluminescence enhancement and changes their spectrum emission. Our research shows that etching the shell of these nanowires nanocrystals leads to their deviation from the vertical position.

The self-assembled InAs quantum dots (QDs) in silicon were fabricated by solid source molecular beam epitaxy on $\mathrm{Si}(\mathbf{1 0 0}) 4^{\circ}$ substrates using Wolmer-Veber growth mode. The PL spectra exhibit $1.6 \mu \mathrm{m}$ emission from InAs quantum dots at 10 K. The size-depended luminescence behavior of QDs was observed. As the InAs coverage decreased from 2 to 0.5 monolayers (ML), the photoluminescence peak shifted from 1620 to 1580 nm and increased monotonously.

The features of photoluminescence (PL) of hybrid nanostructures based on InP/InAsP/InP nanowires array with deposited colloidal CdSe/ZnS-trioctylphosphine oxide quantum dots at increasing pump power have been studied. Pumping was carried out by 10 ps laser pulses duration with 1 MHz repetition rate at 532 nm wavelength in the quasi-resonant region of QDs absorption. It has been established, that PL maximum of the nanostructure shifts hypsochromically with increasing of laser power, revealing a gradual dominance of the bands of its components. This PL manifestation is explained by the cascade filling of excited excitonic states, accompanied by the Auger recombination processes and light quenching. The role of free carriers absorption and energy exchange between excitonic states at high pump intensities is noted, as well as a sharp PL duration reduction associated with an increase of stimulated processes in absorption.

We present the results of experimental studies on the synthesis by molecular-beam epitaxy of AlGaAs nanowires with InAs quantum dots. The morphological, structural, and optical properties of the grown nanostructures have been studied. It is important to note that the emission from quantum dots is observed in the wavelength range from 750 to 970 nm. Assumptions about the nature of short-wavelength emission from quantum dots are formulated. In particular, one of the reasons may be a significant desorption of indium atoms and the presence of gallium atoms in catalyst drops during the growth at a substrate temperature of 510◦C. The proposed technology opens up new possibilities for integration direct-gap III−V materials with a silicon platform for various applications in photonics and quantum communications.

In this work, we propose a simple method to enhance the photoluminescence of InGaN nanowires using CdSe/ZnS colloidal quantum dots. It is found that decoration the surface of InGaN NWs with QDs leads to an increase in the integral and peak photoluminescence intensity by more than 3 times. The observed enhancement is attributed to the nonradiative energy transfer between quantum dots and nanowires.

AlGaAs nanowires with InAs quantum dots on the silicon surface were synthesized by molecular-beam epitaxy. Morphological and optical properties of grown nanostructures were studied. It is important to note, that emission from quantum dots is observed in the wavelength range from 780 to 970 nm. Assumptions about the nature of short-wave radiation from quan-tum dots were formulated. In particular, one of the reasons may be the significant desorption of indium atoms and the presence of gallium atoms in the catalyst droplets during growth at the substrate temperature of 510 degrees C. Our work, therefore, opens new prospects for integration of direct bandgap semiconductors with silicon platform.

We investigate the photoluminescence of a film obtained by the uniform deposition of a colloidal solution of CdSe/ZnS quantum dots capped by trioctylphosphine oxide on an array of isolated InP/InAsP/InP nanowires and subsequently removed from the substrate. The photoluminescence spectrum of the film shows emission bands corresponding to InAsP nano-insertions (1.25-1.5 mu m) and quantum wells (1.0-1.2 mu m). We find that the dependence of the photoluminescence intensity on the excitation intensity has a nonlinear character, which we interpret as a manifestation of the light quenching effect, and that the photodynamics of excitation of the nano insertions and quantum wells differ from each other. We analyse the light quenching effect taking into account the significant increase in the luminescence intensity observed in such hybrid film as compared to an array of isolated InP/InAsP/InP nanowires. We hypothesize the possible suppression of Auger relaxation due to multistep nonradiative transfer of excitation.

Subject of study. The dependence of the photoluminescence of a flexible film structure, which is an array of InP/InAsP/InP nanowires incorporated into a polymerized trioctylphosphine oxide layer with CdSe/ZnS colloidal quantum dots, on the intensity of excitation in the near-infrared range at room temperature was investigated in this study. Method. Nanowires were synthesized on a Si (III) substrate by molecular beam epitaxy using a Riber Compact 21 setup. A polymerized film formed after application of a colloidal solution of trioctylphosphine oxide and CdSe/ZnS quantum dots in toluene on the substrate. This film could be easily detached from the substrate. A continuous Nd+3:yttrium lithium fluoride laser with a wavelength of 527 nm acted as an excitation source in spectral measurements. The emission power varied in the range of 15-100 mW. Main results. A method for fabrication of a flexible film structure comprising an array of semiconductor nanowires and colloidal quantum dots was demonstrated. A nonlinear dependence of the photoluminescence intensity on the intensity of exciting radiation was obtained. It was attributed to the light quenching effect. A mechanism for the increase in the photoluminescence intensity in the film structure is proposed. Practical significance. Considering the position of the maximum in the photoluminescence band in the vicinity of 1.3 mu m, the proposed film heterostructure can be advantageous for integration with fiber-optic systems. (C) 2022 Optica Publishing Group

The results of experimental studies on the synthesis by molecular-beam epitaxy of AlGaAs nanowires with InGaAs quantum dots are presented. It was shown that, as in the case of the InP/InAsP material system, the formation of predominantly two objects is observed in the body of AlGaAs nanowire: InGaAs quantum dot due to axial growth and InGaAs quantum well due to radial growth. It is important to note that the grown nanostructures were formed predominantly in the wurtzite crystallographic phase. The results of the grown nanostructures physical properties studies indicate that they are promising for moving single-photon sources to the long-wavelength region. The proposed technology opens up new possibilities for integration direct-gap III-V materials with a silicon platform for various applications in photonics and quantum communications. Keywords: semiconductors, nanowires, quantum dots, III-V compounds, silicon, molecular-beam epitaxy.

The results of experimental studies on the synthesis by molecular-beam epitaxy of AlGaAs nanowires with InGaAs quantum dots are presented. It was shown that, as in the case of the InP/InAsP material system, the formation of predominantly two objects is observed in the body of AlGaAs nanowire: InGaAs quantum dot due to axial growth and InGaAs quantum well due to radial growth. It is important to note that the grown nanostructures were formed predominantly in the wurtzite crystallographic phase. The results of the grown nanostructures physical properties studies indicate that they are promising for moving single-photon sources to the long-wavelength region. The proposed technology opens up new possibilities for integration direct-gap III−V materials with a silicon platform for various applications in photonics and quantum communications.

The development of a new semiconductor element base is necessary to create a new generation of applications. At present time, the synthesis of high-quality hybrid nanostructures based on III-V quantum dots in the body of nanowires of a wide range of material systems is an urgent and important task. In work hybrid III-V nanostructures based on QDs in the body of NWs in GaP/GaAs and AlGaP/InGaP material systems were synthesized in on silicon substrates and their physical properties were investigated.

We demonstrate growth of AlGaAs NWs with GaAs QDs and InP NWs with InAsP QDs on silicon substrates. Results of GaAs QDs optical properties study have shown that these objects are sources of single photons. In case of InP NWs with InAsP QDs, the results showed that ~ 100% of homogeneously oriented NWs were formed with good optical quality of this system on a Si(111). PL spectrum peak near 1.3 μm indicates that such system is promising for optoelectronic devices.

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 possibility of AlGaAs nanowires with GaAs quantum dots and InP nanowires with InAsP quantum dots growth by molecular-beam epitaxy on silicon substrates has been demonstrated. Results of GaAs quantum dots optical properties studies have shown that these objects are sources of single photons. In case of InP nanowires with InAsP quantum dots, the results we obtained indicate that nearly 100% of coherent nanowires can be formed with high optical quality of this system on a silicon surface. The presence of a band with maximum emission intensity near 1.3 μm makes it possible to consider the given system promising for further integration of optical elements on silicon platform with fiber-optic systems. Our work, therefore, opens new prospects for integration of direct bandgap semiconductors and singlephoton sources on silicon platform for various applications in the fields of silicon photonics and quantum information technology.

The luminescence photodynamics of an array of InP/InAsP/InP nanowires formed via molecular beam epitaxy onto a Si(III) substrate is investigated in this work. Using several kinetic models, the experimental data acquired by a 633-nm room-temperature laser excitation have been analyzed. The kinetics of luminescence decay of the InAsP nanoinsert is shown to be best described in the context of the model of contact quenching. The total time of decay of the excited state (the radiative lifetime) of the InAsP nanoinsert is estimated to be τ ~ 40 ns. The reasons of unexpectedly long duration of the excitation transfer from InP are discussed as well.