The epitaxial growth technique of InGaAs photodiode structures based on a digital InGaAs/GaAs metamorphic buffer layer by metalorganic chemical vapor deposition has been developed. The spectral dependence of the photocurrent of photodiodes based on the produced structures has a maximum at the 1.16 µm wavelength. The photosensitivity range at 10% of peak is 0.99 - 1.33 µm at room temperature. The current-voltage characteristics in the temperature range 9–300 K were investigated. It is shown that the dark current consists of generation-recombination and tunneling components. The dark current density at room temperature was 8×10 -5 A/cm 2 with a reverse bias of -5 V.

The work examines the features of the magnetotransport and magnetooptical properties of a GaAs structure with a Mn S-layer located near an In0.25Ga0.75As/GaAs quantum well with high charge carrier mobility. It is shown that in the initial structure, conduction occurs predominantly in the quantum well region, that leads to the dominance of magnetotransport phenomena of a Lorentzian nature (ordinary Hall effect and positive magnetoresistance). After suppression of the conduction channel through the quantum well using ion irradiation, an anomalous Hall effect and negative resistance are observed. It has been established that the experimental magnetic field dependences of the Hall resistance in ferromagnetic nanostructures with multiple conduction channels may not reflect the real magnetic properties of the structures.

Hybrid structures combining ferromagnetic (FM) and semiconductor constituents have great potential for future applications in the field of spintronics. A systematic approach to study spin-dependent transport in a GaMnAs/GaAs/InGaAs quantum well (QW) hybrid structure with a few-nanometer-thick GaAs barrier is developed. It is demonstrated that a combination of spin electromotive force measurements and photoluminescence detection provides a powerful tool for studying the properties of such hybrid structures and allows the resolution of the dynamic FM proximity effect on a nanometer scale. The method can be generalized to various systems, including rapidly developing 2D van der Waals materials.

The properties of carbon layers (C-layers) formed by thermal decomposition of CCl4 at temperatures of 600-700oC on the surface of gallium arsenide structures fabricated by MOC-hydride epitaxy on n+-GaAs (100) wafers have been studied. The surface morphology of the carbon layers was studied using atomic force microscopy. The structural and optical properties were studied using Raman spectroscopy and reflection spectroscopy. It has been found that in the case of a C-layer fabricated at a temperature of 650-700oC, the atomic force microscopy image demonstrates the presence of vertical carbon nanowalls (vertical graphene) located parallel to one of the [110] directions of the GaAs crystal lattice. The characteristics of the bands observed in the Raman spectra correspond to the parameters of the spectra of vertical graphene. The reflectivity coefficient of such carbon layers significantly decreases (diffuse reflection does not exceed 25% for a layer fabricated at 700oC) in the wavelength range from 0.19 to 1.8 μm. The presence of a significant "absorbing" ability makes the obtained carbon layers promising as a conducting contact in photosensitive semiconductor device structures, which is confirmed by preliminary results of studies of the current-voltage characteristics and spectral dependences of the photocurrent. Keywords: thermal decomposition of carbon tetrachloride, gallium arsenide, vertical graphene morphology.

The results of studies of InP/GaAs heterostructures based on metamorphic layers with stepwise and digital changes in composition are presented. The electrophysical characteristics of diodes fabricated based on these structures are compared with diodes grown on matched substrates with InP and GaAs active layers. It is shown that the use of InP/GaAs diodes in a triple balanced mixer made it possible to reduce the local oscillator signal power by a factor of 20.

The properties of carbon layers (C- layers) formed by thermal decomposition of CCl4 at temperatures of 600–700°C on the surface of gallium arsenide structures fabricated by MOС-hydride epitaxy on n+-GaAs (100) wafers have been studied. The surface morphology of the carbon layers was studied using atomic force microscopy. The structural and optical properties were studied using Raman spectroscopy and reflection spectroscopy. It has been found that in the case of a C layer fabricated at a temperature of 650–700°C, the atomic force microscopy image demonstrates the presence of vertical carbon nanowalls (vertical graphene) located parallel to one of the [110] directions of the GaAs crystal lattice. The characteristics of the bands observed in the Raman spectra correspond to the parameters of the spectra of vertical graphene. The reflection coefficient of such carbon layers significantly decreases (diffuse reflection does not exceed 25% for a layer fabricated at 700°C) in the wavelength range from 0.19 to 1.8 μm. The presence of a significant "absorbing" ability makes the obtained carbon layers promising as a conducting contact in photosensitive semiconductor device structures, which is confirmed by preliminary results of studies of the current-voltage characteristics and spectral dependences of the photocurrent.

Operation modes of laser structures with controlled polarization of light have been studied and the results of measuring polarization characteristics are presented. The possibility of controlling both the linear and circular polarizations of light with corresponding modification of the laser design is shown. In particular, stable lasing at two orthogonally polarized modes in the near-IR range with the intensity ratio of radiation components ITE/ITM ≈ 4.5 is implemented. The possibility is confirmed of generation of circularly polarized radiation in edge-emitting laser diodes by magnetization of a combined semitransparent mirror with a ferromagnetic CoPt layer deposited on the end face of the laser cavity. The degree of polarization is ±1.25% in the CoPt layer saturation magnetization mode.

The GaAs semiconductor structures for the application as betavoltaic power sources were investigated. Three types of structures underwent a comparative study: a Schottky diode, a p-n junction and Schottky structure modified by deposition of a carbon layer. The power characteristics were estimated by Monte-Carlo simulation and collected current calculation using parameters obtained from the electron beam induced current technique. It was shown that carbon deposition on the top of n-GaAs allows passivating the surface states and thus improving betavoltaic performance.

We have investigated the layers of the (Ga,Mn)As diluted magnetic semiconductor with the thickness in the range of 150 - 400 nm, which have been formed by the combination of the methods of a pulsed laser deposition and a post-growth pulsed laser annealing. It has been found that the laser annealing has a significant effect on the structural, magnetic, and electrical properties of the thinnest (~150 nm) (Ga,Mn)As layer. For this layer the additional activation of the Mn impurity, the Curie temperature increase and the dissolution of the second phase MnAs clusters have been observed. The results of model calculations of heat spread in (Ga,Mn)As layer have shown that in thicker layers a MnAs melting point temperature is not achievable (for the chosen conditions of pulsed laser annealing) in the entire layer.

The spin-memory effect in the GaAs / InGaAs heterostructures with $\delta$ layer in GaAs barrier have been investigated. The effect consists in spin polarization of Mn atoms due to interaction with photogenerated spin-polarized holes. The investigation of the effect was carried out by analyzing the polarization of the probe photoluminescence pulse in the pump-probe technique. It was shown that the circular polarization degree of probe pulse generated photoluminescence is strongly affected by the interaction of hole spins with spins of Mn atoms polarized by the pump pulse. The latter leads to decrease of circular polarization degree as compared with single pulse excitation ($\delta P$ effect). The amplitude of $\delta P$-effect is most strongly affected by the concentration of resident electrons in the quantum well which is believed to be due the specific compliance with selection rules for optical transition with the participation of unpolarized resident electrons. The rest of the sample's parameters including the spatial separation between $\delta$ layer and InGaAs quantum well ($d_s$) have a minor effect on the $\delta P$ value which leads to a paradoxical situation of decreasing $\delta P$-effect with the decrease of $d_s$. The proposed experimental technique consisting in creating the significant concentration of resident electrons in the QW may serve as a reliable photoluminescence method determining the strength of this effect as well as the Mn spin relaxation time in a particular nanostructure.

Using a combination of MOC-hydride epitaxy and pulsed laser deposition, InGaAs/GaAs heteronanostructures with a (Ga,Mn)As layer on the surface are obtained, and the influence of the action of a pulsed excimer laser (with a wavelength of 248 nm, pulse duration of ~30 ns, and energy density in the range of 200–360 mJ/cm2) on their radiative, structural, and galvanomagnetic properties is studied. The study is carried out using photoluminescence spectroscopy complemented by the possibility of analyzing radiation polarization characteristics of the structures. The crystalline perfection of the initial and laser-irradiated samples was studied with the use of Raman scattering spectroscopy. The elementary composition of the structures and its distribution over the depth were studied by secondary ion mass spectrometry. The influence of pulsed laser annealing on ferromagnetic properties of heteronanostructures is characterized by the behavior of magnetic field dependences of the Hall resistance and magnetoresistance at temperatures of 10–300 K within the range of magnetic fields of ±3600 Oe. At room temperature, the study was carried out in magnetic fields reaching ±28 000 Oe. The calculated temperature distributions along the sample thickness and in time using the laser annealing model based on solving the problem about heat propagation in a one-dimensional GaAs system with allowance for the (Ga,Mn)As layer on the surface are obtained using original data on the thermal conductivity of structures with a (Ga,Mn)As layer. The data were obtained by the modified frequency division technique (the 3ω method).

Приведены результаты исследования режимов работы лазерных структур с управляемой поляризацией света, в том числе результаты измерения поляризационных характеристик. Показана возможность управления как линейной, так и циркулярной поляризацией света при соответствующей модификации конструкции лазера. В частности, осуществлена устойчивая лазерная генерация на двух ортогонально-поляризованных модах в ближнем ИК диапазоне с соотношением интенсивностей компонент излучения ITE/ITM~ 4.5. Реализована возможность генерации циркулярно-поляризованного излучения в торцевых лазерных диодах посредством намагничивания комбинированного полупрозрачного зеркала с ферромагнитным слоем CoPt, нанесенного на торец лазерного резонатора. В режиме насыщения намагниченности слоя CoPt значение степени поляризации составило ±1.25%. Ключевые слова: полупроводники, лазерный диод, квантовая яма, поляризация.

Управление поляризацией лазерного излучения – одна из важнейших практических задач радиофотоники, оптоэлектроники и спинтроники [1, 2]. В настоящей работе представлены результаты исследований гетеролазеров, предназначенных для генерации циркулярно-поляризованного излучения, работающих в области ближнего ИК диапазона при 300К. Для создания таких лазеров использован новый подход, основанный на формировании ферромагнитного зеркала лазерного резонатора. Спин-зависимое отражение/пропускание лазерного излучения ферромагнитным зеркалом обусловливает появление в излучении циркулярно-поляризованной компоненты [3].

Diode structures with ferromagnetic narrow-gap semiconductors A3FeB5 as only p-region (p-GaFeSb/n-InGaAs), only n-region (n-InFeSb/p-InGaAs), p- and n-regions (p-GaFeSb/n-InFeSb, p-GaFeSb/n-InFeAs) for p-n junction were fabricated by pulsed laser deposition in vacuum. The composition of ferromagnetic semiconductor layers and their thicknesses, determined by X-ray photoelectron spectroscopy, generally correspond to the technological data for diode structures. In particular, the thickness of the GaFeSb layer is 25–30 nm, and the thickness of the InFeAs and InFeSb layers is 35–40 nm. The iron content in InFeSb ranges from 25 to 35 at.%. The GaFeSb layer contains from 15 to 41 iron at. %, and the InFeAs layer - 35 iron at. %. The chemical analysis of the structures revealed the presence of chemical bonds Fe-As (Sb), In-Fe and Fe-Ga. Therefore, it can be assumed that Fe atoms in the fabricated structures can substitute for elements of groups III and V simultaneously. All structures exhibit the effect of negative magnetoresistance at sufficiently low observation voltages of the effect (up to 50 mV), in low magnetic fields (up to 3600 Oe), and at high measurement temperatures. For GaFeSb/InFeSb, GaFeSb/InFeAs diodes, negative magnetoresistance was first observed at room temperature. The hysteresis form of the dependences of the resistance on the magnetic field suggests the effect of the ferromagnetic properties of the layers of narrow-gap semiconductors on the transport of carriers in the structures.

The possibility of modifying the properties of a (Ga,Mn)As layer on the surface of a quantum-size InGaAs/GaAs-structure by laser annealing with the conservation of its emitting properties is studied. To perform these studies by a combination of the methods of MOC-hydride epitaxy and pulsed laser deposition, the structures have been prepared with four quantum wells InGaAs/GaAs (indium contents from 0.08 to 0.25) located at various distances from the (Ga,Mn)As layer. The radiation energy density of an LPX-200 pulsed excimer laser was varied during the experiments from 200 to 360 mJ/cm2, and the depth of the laser action was determined from the changes in the photoluminescence spectra of the quantum wells. The results are described using the laser annealing model based on the solution of the problem of heat propagation in a one-dimensional GaAs system, taking into account a (Ga,Mn)As layer on the surface. The changes in the structural and galvanomagnetic properties of the samples under action of laser irradiation are analyzed. It is shown that the pulsed laser irradiation with the laser radiation energy density 250–300 mJ/cm2 enable one to conserve the emitting properties of the active region (quantum wells InGaAs/GaAs) disposed at the distances 10–12 nm from the (Ga,Mn)As layer and to modify the ferromagnetic properties of the (Ga,Mn)As semiconductor, namely, to increase the ferromagnet–paramagnet phase transition temperature to values no lower than 120 K. The results are promising for the development of the technology of devices of spin optoelectronics.

The diode structures with narrow-gap ferromagnetic A3FeB5 semiconductors in the function of only p-region (p-GaFeSb/n-InGaAs), only n-region (n-InFeSb/p-InGaAs), p- and n-regions (p‑GaFeSb/ n-InFeSb, p-GaFeSb/n-InFeAs) of the p–n junction were manufactured by the method of pulsed laser deposition in vacuum. Composition of the ferromagnetic semiconductor layers and their thicknesses determined by the results of X-ray photoelectron spectroscopy in total correspond to the technological information for diode structures. More specifically, thickness of the GaFeSb layer is 25–30 nm, thicknesses of the InFeAs and InFeSb layers is 35–40 nm. The iron content in InFeSb ranges from 25 to 35 at %. The GaFeSb layer contains from 15 to 41 at % of iron, while 35 at % of iron is registered in InFeAs layer. Presence of Fe‒As(Sb), In–Fe, and Fe–Ga chemical bonds was found at chemical analysis of the structures. Because of this, it may be assumed that, in the manufactured structures, the Fe atoms can displace the elements of III and V groups simultaneously. All the structures demonstrates the effect of negative magnetoresistance at sufficiently low potentials of observation of the effect (to 50 mV), in small magnetic fields (to 3600 Oe) and at high temperature of measurements. For the GaFeSb/InFeSb, GaFeSb/InFeAs diodes, the negative magnetoresistance was observed for the first time up to room temperature. The hysteresis form of the dependences of resistance on magnetic field suggests an effect of ferromagnetic properties of the narrow-gap semiconductor layers on the carrier transport in the structures.

InGaAs/GaAs heteronanostructures with a (Ga,Mn)As layer on the surface were fabricated by MOCVD epitaxy and pulsed laser deposition, and the effect of a pulsed excimer laser (wavelength 248 nm, pulse duration ~ 30 ns) on their radiative, structural and galvanomagnetic properties was studied. The radiation energy density was varied in the range from 200 to 360 mJ/cm2. In the studies, photoluminescence spectroscopy was used, which makes it possible to analyze the polarization characteristics of the radiation of the structures. The crystalline perfection of the initial and laser-irradiated samples was studied using Raman spectroscopy. The elemental composition of the structures and its depth distribution were studied by secondary ion mass spectrometry. The effect of pulsed laser annealing on the ferromagnetic properties of heteronanostructures was characterized by the behavior of the magnetic field dependences of the Hall resistance and magnetoresistance at temperatures of 10–300 K in the range of magnetic fields ± 3600 Oe. At room temperature, the study was carried out in magnetic fields reaching values of ± 28000 Oe. To obtain the calculated temperature distributions along the sample thickness and in time using a model of the laser annealing process based on solving the problem of heat propagation in a one-dimensional GaAs system taking into account the (Ga,Mn)As layer on the surface, we used the original data on the thermal conductivity coefficient of structures with a layer (Ga,Mn)As obtained using a modified frequency separation technique (3ω-method).

It was studied the possibility of laser annealing modification of the properties of the (Ga,Mn)As layer located on the surface of a quantum-well InGaAs/GaAs structure, while retaining its radiative properties. The structures with four InGaAs/GaAs quantum wells (indium content was varied from 0.08 to 0.25), located at different distances from the (Ga,Mn)As layer, were fabricated by combining the methods of MOCVD-hydride epitaxy and pulsed laser deposition. The LPX-200 excimer laser pulse energy density was varied from 200 to 360 mJ/cm2, and the depth of laser action was determined from the change in the photoluminescence spectra of the quantum wells. In describing the results obtained, a model of the laser annealing process was used, based on solving the problem of heat propagation in a one-dimensional GaAs system, taking into account the (Ga,Mn)As layer on the surface. Changes in the structural and galvanomagnetic properties of the samples as a result of laser irradiation were analyzed. It is shown that as a result of pulsed laser action at a laser energy density range of 250 - 300 mJ/cm2, it is possible to preserve the emissive properties of the active region (InGaAs/GaAs quantum well) located at a distance of 10 - 12 nm from the (Ga,Mn)As layer and modify ferromagnetic properties of the semiconductor (Ga,Mn)As, namely: to increase the temperature of the ferromagnet-paramagnetic phase transition to values of at least 120 K. The results obtained are promising for the development of technology for devices of spin optoelectronics.

Abstract A new method for depositing carbon films by the thermal decomposition of carbon tetrachloride (CCl_4) in a hydrogen flux in a reactor for metal-organic chemical vapor deposition (MOCVD) at atmospheric pressure is developed. From the results obtained by Raman spectroscopy, it can be conceived that the carbon layers produced by this method are the disordered nanocrystalline graphite. It is shown that such carbon layers can be used in the technological cycle of the production of gallium-arsenide optoelectronic device structures (among them spin light-emitting diodes with a CoPt injector).

The effects of KrF excimer laser pulses on the crystalline and optical properties of structures with four InxGa1−xAs/GaAs quantum wells (x ranged from 0.08 to 0.25) were studied. The results obtained by Raman spectroscopy and reflection spectroscopy showed that the high crystalline quality of the GaAs cap layer is retained after exposure to laser radiation with an energy density of 200 to 360 mJ/cm2. It was established experimentally by photoluminescence spectroscopy and by modeling the laser annealing process, which is a solution to the problem of heat propagation in a one-dimensional GaAs-based system, that the thermal effects that occur in heterostructures under pulsed laser irradiation below the GaAs melting threshold lead to relaxation of mechanical stresses. At the initial stages of this process, the point defects appear in InxGa1−xAs/GaAs quantum wells. The latter lead to a “red” shift of the photoluminescence emission peaks of quantum wells and serve as centers of nonradiative recombination, which causes the quenching of the photoluminescence.