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.

The effect of cooling conditions in the plasma-assisted molecular-beam epitaxy growth on the structural and optical properties of InGaN nanostructures is studied. It is shown that cooling of the samples without nitrogen plasma contributes to the suppression of phase separation in InGaN nanostructures. The integrated intensity of photoluminescence from these nanostructures increased by a factor of 2.

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.

We present the results on experimental studies of the directional radiation from GaAs quantum dots in AlGaAs nanowires grown by molecular beam epitaxy technique on silicon surface. It was shown that the radiation intensity from GaAs quantum dots in the direction of nanowires growth is 2 orders of magnitude higher than the intensity of radiation in the perpendicular direction.

Experimental results of studying the germanium deposition on the surface of AlGaAs nanowires are presented. The formation of both cubic and hexagonal Ge phases was revealed using Raman spectroscopy. The inheritance of the crystal structure during the growth of thin germanium layers on the lateral surfaces of wurtzite nanowires was shown.

The spontaneous synthesis of InGaN/GaN nanowires of core-shell heterostructure using molecular beam epitaxy isinvestigated in the work. It is shown by electron microscopy that a wedge-shaped crack can form at In content x=0.4 and 0.04 in the core and shell correspondent. Based on the model of internal structural stresses, a formula is proposed for estimation of the critical size and composition for the formation of cracks in NWs.The estimations and experimental data of morphology agree with each other.

In this work, InGaN nanowires with a high In content were grown, for the first time, on hybrid SiC/Si substrates and compared with InGaN nanowires grown on Si. It was shown that InGaN nanowires on SiC/Si have lower indium content (by about 10%) compared to the nanowires on Si. The results can be beneficial for studying the growth mechanisms of InGaN nanowires and creating optoelectronic devices in the visible spectral range.

Using spectral ellipsometry, Raman spectroscopy, and scanning microscopy with an X-ray spectrometer (EDS), the phenomenon of self-organized change in the composition of AlxGa1-xN epitaxial layers during their growth by chloride-hydride epitaxy (EDX) on SiC / Si (111) hybrid substrates was revealed. It was found that during the growth of AlxGa1-xN layers with a low, about 11-24% Al content, interlayers (domains) appear, consisting of AlGaN stoichiometric composition. A qualitative model has been proposed, according to which self-organization in composition arises due to the effect of two processes on the growth kinetics of the AlxGa1-xN film. The first process is associated with the competition of two chemical reactions proceeding at different rates. One of these reactions is the AlN formation reaction; the second is the reaction of GaN formation. The second process, closely related to the first, is the appearance of elastic compressive and tensile stresses during the growth of AlxGa1-xN films by the CGE method on SiC / Si (111). Both processes influence each other, which leads to a complex pattern of aperiodic changes in the composition over the thickness of the film layer. Keywords: A3B5 compounds, wide-gap semiconductors, AlGaN, AlN, GaN, silicon carbide on silicon, self-organization of the composition, HVPE method, solid solutions, heterostructures.

In this work, the influence of substrate temperature on morphological and optical properties of branched InGaN nanostructures on the Si(111) surface during MBE growth was studied. It was shown that an increase of the substrate temperature leads to a change in the morphology of InGaN nanostructures. In particular, the height of InGaN nanocolumns, which are formed at the initial stage of growth, increases. At the same time, an increase in the growth temperature of InGaN nanostructures leads to an increase in the intensity of the photoluminescence spectra from such structures, and the dependences of the integrated photoluminescence intensity on the excitation power are linear in both cases. All these facts indicate the promise of such structures for optical applications, for example, for creating white LEDs based on a single material

The spectral and nonlinear optical properties of InAs nanowires suspensions in isopropanol were studied at room temperature. InAs nanowires were synthesized by molecular beam epitaxy. The absorption spectra of suspensions with a characteristic maximum at a wavelength of 235 nm were obtained, as well as Raman spectra in the range 180–280 cm – 1. The nonlinear transmission of InAs nanowires with a diameter less than the Bohr radius of the exciton upon two-photon excitation in the transparency region in the visible range (λ = 468 nm) was studied firstly. The effect of cumulative bleaching was discovered, the manifestation of which is associated with the dynamic Stark effect.

We present the results on the selective-area growth of GaN nanowires using a molecular beam epitaxy technique on patterned SiOx/Si substrates without any seed layers. The patterned SiOx/Si substrates were prepared by the simple microlens photolithography method. The influence of the substrate temperature on the morphological properties of GaN nanowires was investigated. The optimal growth parameters for the selective-area growth of GaN nanowires were experimentally determined.

A possibility of InGaN «nanoflowers» MBE growth on Si substrate has been demonstrated. The results of morphological studies have shown that InGaN synthesis occurs in several stages even at constant substrate temperature. The grown structures show wide photoluminescence spectrum in the range from 450 to 950 nm at room temperature.

AbstractThe time evolution of the ensemble of micropores formed in the near-surface region of silicon during the growth of thin films of silicon carbide is studied by the method of atom substitution. SiC/Si samples are studied by scanning electron microscopy, ellipsometry, and confocal Raman microscopy. The formation of the porous layer involves several characteristic stages: the emergence of single pores, their growth with the formation of dendrite-like structures, and subsequent coalescence into a continuous layer. It is shown that the thickness of the porous layer at the initial stages of the growth is proportional to the cubic root of time. The possible mechanisms of pore formation are discussed and a theoretical model is proposed to describe the dependence of the average thickness of the porous layer on time. The model is in a good qualitative agreement with the experimental results.

AbstractThe possibility in principle of the MBE (molecular-beam epitaxy) growth of GaP and InP nanowires on a SiC substrate with a graphene layer is demonstrated for the first time. InP nanowires on such a substrate have no stacking faults and possess an ideal crystallographic quality. At the same time, GaP nanowires have structural defects of the type of twins and the reversal of crystallographic phases at the top and at the base. The results of structural measurements demonstrate that the nanowires are formed in the wurtzite phase, which is not typical of bulk III–V materials.

AbstractData on the growth and physical properties of nanostructures of the type “InAsP insert embedded in InP nanowire (NW)” grown on Si (111) surfaces by Au-assisted molecular-beam epitaxy are presented. It is found that nearly 100%-coherent NWs can be grown with a widely varying surface density. A relationship between the optical and structural properties of the NWs is revealed. It is shown that the NWs under study are formed of a purely wurtzite phase. The suggested technology opens up new opportunities for the integration of direct-gap III–V materials and silicon.

AbstractArrays of Be-doped (Al,Ga)As core/shell nanowires are synthesized by molecular-beam epitaxy on a Si-doped n -GaAs (111)B substrate. A study of the photovoltaic properties of the structures under illumination with a solar simulator (AM1.5G spectrum) demonstrate that the internal quantum efficiency of the resulting solar cell is 4 . 1%, and its power conversion efficiency is 0.4%.

AbstractIn the work we investigate synthesis of aluminum nitride films using reactive ion plasma deposition in oxygen/nitrogen gas mixture for application as optical elements for power semiconductor lasers. The experimental refractive index of synthesized AlNO films is dependent on oxygen composition and is decreasing in diapason from 1.76 to 2.035 at elevation of the oxygen fraction.It is shown that the AlN films synthesized by pure nitrogen plasma are polycrystalline and textured. The oxygen presence in discharging gas results to growth of amorphous phase of the AlNO film.

The paper presents studies of the structural and optical properties of AlN thin films grown on an AlGaAs/GaAs semiconductor laser heterostructure with the use of preliminary ionic surface cleaning and without it. After cleavage of the heterostructure, a natural surface oxide forms on the facet. In the paper, the ionic etching regime providing the removal of the surface oxide layer without significant defects in the semiconductor heterostructure is determined.