Fractionally charged magnetoelectron (anyon) complexes formed by the creation of magnetic flux quanta vortices in single-electron states are detected in a three-electron Wigner quantum dot (Wigner-Seitz radius ) using low-temperature (30 K) magnetophotoluminescence spectroscopy measurements. In zero magnetic field, vortices induce their own field , so such vortices and corresponding complexes can be identified as elementary magnetic poles and Dirac anyons (DAs), respectively. In this quantum dot, DA structures with an average number of vortices per electron from 3 to 2/5 and B from -7 to 0 T were identified in the magnetic field range . Spectral data and calculations of electron density distributions using the configurational interaction approach show that at T the structures are triangular molecules with a side of nm and a DA size of similar to 30 nm, whereas at higher field it is a DA puddle of similar to 80 nm, and thus the molecular states are suppressed by the strong magnetic field. The recognition of magnetoelectron complexes as DAs and the observation of the molecular-puddle transition in the DA composites induced by a magnetic field in Wigner quantum dots are important steps in the investigation of these unique magnetoelectronic quantum states that can be exploited in anyon-based quantum computing. We also show the connection of DAs with the quantum Hall effect states, which clarifies unresolved issues in their description.

The influence of reducing carrier of thermal escape rate with temperature decreasing in various channels on the dark saturation current of a GaAs p–n junction with Ga0.8In0.2As quantum dots has been investigated. The dark saturation current has been calculated for temperatures ranging from 20 to 325 K. The calculation was based on the previously discovered current invariant, which determines the dependence of the saturation current on temperature and bandgap energy. The rates of recombination in various channels and their bandgaps were determined by photoluminescence spectra analysis. For various channels, characteristic temperatures were determined, below which thermal escape rate of carriers is practically absent. The saturation current calculation showed that, despite the change in the rate of recombination in different channels, it is determined only by the recombination in the channel with lower bandgap energy.

Optimized photoconverters for operation under high-power laser radiation in the green-red spectral range based on MOCVD-grown GaInP/GaAs heterostructures are fabricated. The Au(Ge)/Ni/Au and Pd/Ge/Au contact systems have been studied to form the front contact grid of devices. As a result, the laser photoconverter with a Pd/Ge/Au contact showed an efficiency of more than 50% up to an incident radiation power density of 30 W/cm 2 with a maximum value of 54.4% under 7 W/cm 2 for laser line with wavelength of 600 nm. Keywords: photoconverter, laser radiation, MOCVD, efficiency, spectral sensitivity.

GaInP-based laser power converters (LPC) structure grown by MOVPE and device chip design have been optimized for operation under high-power lasers of the green-red spectral range. Light I-V curves records have shown the performance of the LPC at up to 40-50 W/cm2 of incident power densities. The highest level data were obtained for 532, 600, and 633 nm power laser lines: 44.3%, 46.7%, and 40.6% under 13-16 W/cm2, respectively. LPC demonstrated an efficiency of more than 40% at the incident laser radiation power density elevated up to 40-50 W/cm2. Keywords: laser photoconverter, MOVPE, efficiency, spectral response.

The effect of positioning of the In0.8Ga0.2As quantum dots (QDs) array in the i-region of the solar cell (SC) on its photogenerated current and dark saturation currents, which determine the device operating voltage, have been investigated. It was found out that the indicated photoelectric characteristics depend on the location of the QD array relative to the electric field of the p-n junction. The displacement of the QD array to the boundary of the weakly doped base leads to a decrease in the photogenerated current. But at the same time, the voltage drop effect, which is well-known for nanoheterostructural SC, is minimal. Keywords: solar cells, quantum dots, dark saturation current

Experiments on the growth of self-assembled InP/GaInP2 quantum dots in dielectric mask 0.1–1 μm apertures by MOVPE epitaxy have been carried out. A sequence of operations for the implementation of the lift-off lithography method is proposed and implemented. The possibility of obtaining apertures with 100 nm diameter and less is shown. Combination of thermally deposited SiO2 and wet etching is shown to produce minimal amount of nonradiative defects and results in a stable PL signal from single QDs in the aperture.

The effect of lattice relaxation instability (martensitic transition) on piezoelectric fields (EPE) in spontaneously ordered GaInP2/GaAs epitaxial layers was demonstrated using scanning Kelvin probe microscopy in combination with electron microscopy and optical spectroscopy measurements. The transition manifests itself in the dependence of the surface potential of the epi-layer on the mechanical (cleavage) and thermal (annealing) impacts. This is associated with a switching of the crystal lattice between relaxed and strained martensitic states, corresponding to a change in EPE in the epi-layer. The measured surface potential values (0.2–2.4 V) correspond to EPE within ±100 kV/cm and a strong decrease in |EPE| with increasing layer thickness, indicating the pinning of the Fermi level and piezoelectric doping. Our results open up the prospects for using spontaneously ordered semiconductor alloys to control electronic states in semiconductor nanostructures by controlling their piezoelectric fields.

The efficiency of GaInP/GaAs/InxGa1-xAs triple-junction solar cells obtained by replacing (in the widely used "classical" GaInP / GaAs / Ge heterostructure) the lower germanium with InxGa1-xAs subcell formed using the metamorphic growth technology has been investigated. Based on an original approach, the optimal indium concentration in the narrow-gap subcell has been found. The main parameters of InxGa1-xAs subcells with an indium concentration from x=0.11 to 0.36 were determined and were used to calculate the IV characteristics of GaInP/GaAs/InxGa1-xAs solar cells. It has been determined that at x=0.28 the efficiency of the triple-junction solar cell increases by 3.4% (abs) in comparison with the "classical" solar cell, reaching a value of 40.3% (AM1.5D). Also it has been shown that the efficiency of such solar cells can be increased up to 41%. Keywords: Multi-junction solar cells, photoconverters, metamorphic buffer. M.Z.Shvarts,

The structure of epitaxial films of the GaInP solid solution, in which ordering occurs, has been studied by transmission electron microscopy. The films have been grown by metalorganic vapor-phase epitaxy on GaAs(001) substrates near the half-composition point. The dark-field images obtained using superstructure reflections for cross-sectional and plane-view samples of films have been analyzed. The morphology and relative spatial arrangement of ordered domains have been determined. The phenomenon of spontaneous self-organization of regions with CuPt–B+ and CuPt–B– ordering near the surface has been discovered, while in the bulk of the film, the domains are uniformly distributed and overlap. The effect of spatial separation of domains is attributed to the misfit stress relaxation in the growing epitaxial layer, which changes the surface topology.

In this work, we studied the influence of GaP compensating layers on the characteristics of GaAs solar cells with InGaAs quantum dot arrays. An increase in the overall level of quantum efficiency in the absorption range of quantum dots (870-1000 nm) by more than 10% has been demonstrated when GaP layers are embedded in GaAs intermediate layer (spacer) of a quantum dot array. It was also shown that in this case a noticeable increase in the open-circuit voltage can be achieved at high solar concentration.

Hybrid organic-inorganic lead halide perovskites (LHP) are gaining considerable attention due to their wide range of potential applications, particularly as an active layer in solar cells and light-emitting devices owing to their excellent light-harvesting and photoluminescence emission properties. Considering their high color purity and color-tunability, high photoluminescence quantum yield (PLQY), easy fabrication, and cost-efficiency, LHP are promising candidates to compete with the traditional active layer in solid-state lighting. The PL emission of CsPbX3 (X = I, Br, Cl) covers the entire visible range from 400 to 730 nm and can be easily tuned via halide replacement in the I <-> Br <-> Cl series. In this work, photoluminescence (PL), luminescence excitation, UV/VIS/ NIR absorption, structural and morphological properties of CsPb(I1-xBrx)3 (x = 0-1) nanosized powders prepared by the mechanochemical synthesis method is investigated at 80K and room temperature. A narrow PL peak with full width at half maximum (FWHM) = 16.5 and 6.6 nm was observed at room temperature and 80K from CsPbBr3, respectively. The relation between structure and optical properties of nanopowders is discussed. It is shown that the halide exchange mechanism is an effective approach for fabrication of defect-free materials.

✉ gruzaa01@gmail.com Abstract. We used the photoluminescence spectra of a single InP/GaInP2 quantum dot with a Wigner-Seitz radius of about 3.4, doped with 4 electrons, to measure the magnetic field dispersion of single quantum states in a range between 0 , 10 T at 30 K. The measurements show the formation of a molecular structure at high temperature and its transition to a pud-dle-like structure with a decrease of localization size from 110 nm to 70 nm. Fock-Darwin spectrum fitting shows a decrease in the cyclotron frequency and magnetic field shift, that are interpreted as the formation of an anyon structure in a QD with fractional charge 1/5, 2/3, 1/2 and a built-in magnetic field of -3T.

Photovoltaic converters of high-power (lambda = 800-860 nm, E-LR = 150-550 W/cm(2)) laser radiation (PhotoVoltaic Laser Power Converters - PVLPCs) based on AlGaAs/GaAs heterostructures grown by metalorganic vapor-phase epitaxy have been developed. To increase the output voltage, the space charge region of p-GaAs/n-AlxGa1-4As heterojunction was shifted to the n-AlxGa1-xAs wide-gap layer with a gradual "x". The technology for embedding a rear reflector based on TiOx/SiO2/Ag into the photovoltaic converter structure by "transferring" the heterostructure to a supporting substrate and the method of bonding to form a monolithic structure of the PVLPC has been elaborated. To operate the heterostructures at an increased power density of laser radiation, they have been designed to eliminate possible potential barriers at the heterointerfaces and the frontal contact topology with a high density of the metal grid (50 mu m and 125 mu m contact pitch are under consideration) has been employed. PVLPCs with efficiency of 62% were obtained at the power density of monochromatic radiation (lambda = 850 nm) E-LR = 170 W/cm(2). The finger pitch of 50 mu m allows keeping efficiency more than 56% even with a fivefold increase in laser radiation (up to E-LR = 500 W/cm(2)).

Изготовлены оптимизированные фотопреобразователи на основе гетероструктур GaInP/GaAs, выращенных методом металлоорганической газофазной эпитаксии, для работы с лазерным излучением высокой мощности зелено-красного спектрального диапазона. Для формирования лицевой контактной сетки приборов исследованы контактные системы Au(Ge)/Ni/Au и Pd/Ge/Au. В результате фотопреобразователь лазерной линии с длиной волны 600 nm с Pd/Ge/Au-контактом демонстрировал КПД более 50% вплоть до плотности мощности падающего излучения 30 W/cm 2 с максимальным значением 54.4% при 7 W/cm 2 . Ключевые слова: фотопреобразователь, лазерное излучение, металлоорганическая газофазная эпитаксия (МОСГФЭ), КПД, спектральная чувствительность.

We report non-contact local doping of a monolayer WSe2 transferred onto a piezoelectric substrate having surface potential wells (SPWs) induced by structural inhomogeneities. We used epitaxial GaN and InP/GaInP2 structures, in which there are SPWs ∼0.2 V deep and 0.1–2 μm in size. Using surface topography and potential scanning probe microscopy, as well as optical reflectance, photoluminescence, and Raman spectroscopy measurements, we observed strong enhancement of charged exciton emission and Raman intensity in the SPW regions of the monolayer WSe2, which indicate on piezoelectric doping at a level n ≥ 1012 cm−2 on a length scale ∼0.2–1 μm. Our results can be used to create electron/hole quantum puddles with anyon states in transition metal dichalcogenides, promising for the development of room temperature and magnetic-field-free fault-tolerant topological quantum computing.

We demonstrate non-contact local doping of a monolayer WSe2 transferred onto a piezo-electric substrate having structural inhomogeneities using surface topography and potential scanning probe imaging along with photo-luminescence (PL) and Raman spectra mapping. We used a GaN epilayer grown by molecular beam epitaxy, in which surface potential wells having the depth of ~0.2 V and the size of ~1 μm, induced by inversion domains and Ga droplets are formed. In the monolayer WSe2 flake mechanically exfoliated on the epilayer, we observed a strong enhancement of the trion emission and the A1g phonon Raman intensity in the well region, which indicate a local piezo-electric doping of WSe2 at a level n>1012 cm-2. We show that our results can be used to create quantum Hall puddles having fractionally charged magneto-electron/anyon states at room temperature, which are promising for the development of fault-tolerant topological quantum computing.

GaInP-based laser power converters (LPC) structure grown by MOVPE and device chip design have been optimized for operation under high-power lasers of the green-red spectral range. Light IV curves records have shown the performance of the LPC up to 40-50 W/cm2 of incident power densities. The highest level data were obtained for 532 nm, 600 nm, and 633 nm power laser lines: 44.3%, 46.7%, and 40.6% under 13-16 W/cm2, respectively. LPC demonstrated an efficiency of more than 40% at elevated up to 40-50 W/cm2 of the incident laser power density.

In magneto-photoluminescence (magneto-PL) spectra of quasi two-dimensional islands (quantum dots) having seven electrons and Wigner–Seitz radius rs~1.5, we revealed a suppression of magnetic field (B) dispersion, paramagnetic shifts, and jumps of the energy of the emission components for filling factors ν > 1 (B < 10 T). Additionally, we observed B-hysteresis of the jumps and a dependence of all these anomalous features on rs. Using a theoretical description of the magneto-PL spectra and an analysis of the electronic structure of these dots based on the single-particle Fock–Darwin spectrum and many-particle configuration-interaction calculations, we show that these observations can be described by the rs-dependent formation of the anyon (magneto-electron) composites (ACs) involving single-particle states having non-zero angular momentum and that the anyon states observed involve Majorana modes (MMs), including zero-B modes having an equal number of vortexes and anti-vortexes, which can be considered as Majorana anyons. We show that the paramagnetic shift corresponds to a destruction of the equilibrium self-formed ν~5/2 AC by the external magnetic field and that the jumps and their hysteresis can be described in terms of Majorana qubit states controlled by B and rs. Our results show a critical role of quantum confinement in the formation of magneto-electrons and implies the liquid-crystal nature of fractional quantum Hall effect states, the Majorana anyon origin of the states having even ν, i.e., composite fermions, which provide new opportunities for topological quantum computing.

We describe the growth, material characterization, and lasing of InP/GaInP quantum dot (QD) microdisks (diameter D = 2.2 μm, quality factor Q∼9000) with an emission lasing line of 693 nm (77 K). We demonstrate that MOVPE growth can result in two types of InP/GaInP QDs, differing in height (type A h∼5–10 nm, type B h∼20 nm), whose emission has different decay lifetimes (τA=0.6 ns, τB=2.4 ns). We show, importantly for technological microlasing applications, that lasing occurs via the excited states of type A QDs, as inferred from a number of experimental results: power-dependent photoluminescence, time-resolved experiments, and temperature dependence of the generation threshold.

In the work, the effect of In0.8Ga0.2As quantum dots position in the i-region of a GaAs solar cell on its spectral and photoelectric characteristics has been investigated. Three solar cell structures were obtained by metal-organic vapor-phase epitaxy, in which layers of quantum dots were placed in the middle of the i-region and also have been shifted to the base and the emitter. As a result, it has been shown that the solar cell with a quantum dot array shifted to the base demonstrates the smallest open-circuit voltage drop and, accordingly, a higher efficiency value.