2019, Sibirmovsky, Y. D., Kargin, N. I., Vasil'evskii, I. S., Сибирмовский, Юрий Дмитриевич, Каргин, Николай Иванович, Васильевский, Иван Сергеевич

© 2019 IEEE.The problem of modelling the absorption coefficient and refractive index spectra of III-V heterostructures with multiple quantum wells and superlattices under applied electric field is considered. This is a crucial step in the design of efficient and compact electro-optic modulators. The goal of this work is to find a simple, fast and reliable method to qualitatively compare various heterostructure designs. Which is why two-band effective mass approximation is used here. The paper contains comparison of existing methods as well as some new results.

2020, Adam, P. M., Bardakhanov, S., Movsesyan, A., Khartaeva, E., Nomoev, S., Vasilevskii, I., Номоев, Сергей Андреевич, Васильевский, Иван Сергеевич

© 2020 Author(s).The experiments showed the strong dependence of forward and backward scattering of light in the visible region of the spectrum by silicon nanoparticles on the method of their preparation. Silicon nanoparticles are created in two ways: by laser ablation and by the action of a relativistic electron beam. The backscattering spectra from the obtained silicon nanoparticles were measured. Raman light scattering is much more intense for silicon nanoparticles obtained by an electron beam as compared to those created by laser radiation and from single-crystal silicon. These properties of silicon nanoparticles should be taken into account when creating nanoantennas, metamaterials, and other nanophotonic devices with low dissipative losses and reflection.

2019, Galiev, G. B., Trunkin, I. N., Vasiliev, A. L., Klimov, E. A., Vasil'evskii, I. S., Vinichenko, A. N., Васильевский, Иван Сергеевич, Виниченко, Александр Николаевич

© 2019, Pleiades Publishing, Inc.Abstract: The structural characteristics of a new structure for photoconductive antennas have been investigated. This structure is a multilayered epitaxial film grown on a GaAs(111)A substrate; it consists of alternating undoped low-temperature grown GaAs (LTG-GaAs) layers and GaAs layers synthesized in the standard high-temperature regime and doped with silicon (GaAs:Si). The As4/Ga flow ratio γ is chosen such as to produce p-type GaAs:Si layers. LTG-GaAs layers were grown at an enlarged γ value. The samples grown on GaAs(100) substrates were single-crystal, whereas the single-crystal growth on GaAs(111)A substrates changed to polycrystalline when the film thickness reached 320–340 nm. The sizes of As precipitates in annealed samples, their distribution over the film thickness, and specific features of their crystal structure have been analyzed.

2019, Zinin, P. V., Filonenko, V. P., Fominski, V. Y., Romanov, R. I., Solov'ev, A. A., Vasil'evskii, I. S., Safonov, D. A., Ivanov, A. A., Фоминский, Вячеслав Юрьевич, Романов, Роман Иванович, Соловьев, Алексей, Васильевский, Иван Сергеевич, Сафонов, Данил Андреевич, Иванов, Андрей Анатольевич

© 2019, Pleiades Publishing, Ltd.Abstract: The morphology, chemical composition, microstructure, and electrical properties of BC3 thin films subjected to melting by a nanosecond laser pulse are investigated. The original films have been created by pulsed laser codeposition of B and C onto a sapphire substrate at 150 and 350°C. Morphological changes in the films depended on their initial structural state. However, a “frozen” structure of both films after irradiation corresponded to the B-saturated graphite-like phase, the local composition of which varied due to the formation of inclusions of amorphous boron carbide. Before and after irradiation, the films exhibited a slightly decreasing dependence of the surface resistance with increasing temperature from 4.2 to 330 K. After laser irradiation, the films resistance has decreased by a factor of ~2.6.

2020, Khartaeva, E., Nomoev, S., Vasilevskii, I., Klochkov, A., Vinichenko, A., Номоев, Сергей Андреевич, Васильевский, Иван Сергеевич, Клочков, Алексей Николаевич, Виниченко, Александр Николаевич

© Published under licence by IOP Publishing Ltd.The paper presents the results of numerical simulation of a terahertz (THz) photoconductive antenna with embedded electrodes by the finite element method. The simulation results indicate the fact that the proposed THz antenna has a higher photocurrent than the conventional photoconductive antenna with conventional electrode contacts. Higher THz power can potentially be obtained using the proposed photoconductive antenna with embedded electrodes. The simulation results show that the electric field strength at the surface is higher for conventional PCA, however, the PCA depth with embedded contacts has a higher electric field strength. The simulation results show that the increase in the photocurrent is directly proportional to the thickness of the embedded contacts. The results of the performed experiments are consistent with the conclusions of the simulation.

2020, Klochkov, A. N., Klimov, E. A., Solyankin, P. M., Konnikova, M. R., Vasil'evskii, I. S., Vinichenko, A. N., Васильевский, Иван Сергеевич, Виниченко, Александр Николаевич

© 2020, Pleiades Publishing, Ltd.Abstract: A material in the form of a multilayer structure based on low-temperature LT-GaAs grown on (111)A-oriented substrates is proposed for fabrication of THz photoconductive antennas. These structures contain active LT-GaAs layers and doping acceptor GaAs:Si-based layers. At the optical pump power of 19 mW and the bias voltage of 30 V, a photoconductive antenna based on the optimized {LT-GaAs/GaAs:Si} (111)A structure emits THz pulses with the average power of 2.3 μW at the pulse repetition frequency of 80 MHz; the conversion efficiency is 1.2 × 10–4. It is shown that the dependence of the integral power of THz pulses of the antenna based on the {LT-GaAs/GaAs:Si} (111)A structure on the applied voltage is superlinear; the dependence of this parameter on the optical pump power is plotted as a curve with saturation. It is shown that the designed antennas have a practical application in THz spectroscopy of biological solutions.

2019, Vinichenko, A. N., Safonov, D. A., Kargin, N. I., Vasil'evskii, I. S., Виниченко, Александр Николаевич, Сафонов, Данил Андреевич, Каргин, Николай Иванович, Васильевский, Иван Сергеевич

© 2019, Pleiades Publishing, Ltd. Abstract: Metamorphic high-electron-mobility transistor (HEMT) structures based on deep In 0.2 Ga 0.8 As/In 0.2 Al 0.8 As quantum wells (0.7 eV for Γ electrons) with different metamorphic buffer designs are implemented and investigated for the first time. The electronic properties of metamorphic and pseudomorphic HEMT structures with the same doping are compared. It is found that, over a temperature range of 4–300 K, both the electron mobility and concentration in the HEMT structure with a linear metamorphic buffer are higher than those in the pseudomorphic HEMT structure due to an increase in the depth of the quantum well. Low-temperature magnetotransport measurements demonstrate that the quantum momentum-relaxation time decreases considerably in metamorphic HEMT structures because of enhanced small-angle scattering resulting from structural defects and inhomogeneities, while the dominant scattering mechanism in structures of both types is still due to remote ionized impurities.

2020, Bolshakova, I. A., Kost, Y. Y., Radishevskyi, M. I., Shurygin, F. M., Vasil'evskii, I. S., Васильевский, Иван Сергеевич

© Springer Nature Singapore Pte Ltd. 2020.It was investigated the thermal stability of two types of Hall sensors based on gold nanofilms deposited on sapphire: (i) with the titanium adhesive sublayer (Ti/Au) and (ii) with the titanium adhesive sublayer and the platinum barrier sublayer of (Ti/Pt/Au). Vacuum annealing for 3 h at 400 °C significantly changes all investigated electrophysical parameters of samples with the Ti/Au metallization, which is explained by the titanium diffusion into gold. At the same time, the sensitivity and the resistivity of sensors with the Ti/Pt/Au metallization remain unchanged within a few percent, allowing them to be used in the plasma’s magnetic diagnostic systems of the ITER and DEMO fusion reactors where operating temperatures will exceed 300 °C.

2020, Nomoev, S., Vasilevskii, I., Vinichenko, A., Номоев, Сергей Андреевич, Васильевский, Иван Сергеевич, Виниченко, Александр Николаевич

© 2020 Trans Tech Publications Ltd, SwitzerlandThe design and technological conditions for the manufacture of photoconductive antennas based on low-temperature gallium arsenide (LT-GaAs) have been developed. The optimized photoconductive THz antenna is made based on LT-GaAs with the flag geometry of the contacts and with the interdigitated structure including metal closing through the dielectric of each second period. LT-GaAs samples were obtained by molecular beam epitaxy at temperatures of 210 ̊C, 230 ̊C, 240 ̊C on GaAs substrates (100). Dark and photocurrent were measured depending on the bias voltage of the LT-GaAs heterostructure at the EP6 probe station. Full wave finite element method solver has been used to investigate the proposed plasmon PCA electrical and optical behavior by combining the Maxwell's wave equation with the drift-diffusion/Poisson equations.

2019, Khabibullin, R., Ushakov, D., Afonenko, A., Shchavruk, N., Vasil'Evskii, I., Safonov, D., Васильевский, Иван Сергеевич, Сафонов, Данил Андреевич

© COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.The spectra of mode loss in terahertz quantum cascade laser (THz QCL) with double metal waveguide (DMW) based on Au, Cu and Ag have been analysed. On the basis of measurements of the resistivity of DMW claddings for the temperature range from 4.2 to 300 K, the loss coefficients of THz radiation at Au-, Cu-, Ag-claddings are calculated. We show that the Ag-based DMW allows to reduce the losses by 1.3-7.0 cm-1 in comparison with Au-based DMW at room temperature. Our calculations show that the Ag-based DMW has slightly lower losses (∼1 cm-1) than Cu-based DMW at cryogenic temperatures (below 100 K). The use of Cu-based DMW allows to reduce the loss coefficient in comparison with Ag-based DMW at higher temperatures (above 100 K). Temperature dependence of threshold gain for THz QCL with Au-, Cu-, Ag-based DMW are calculated. Taking into account the absorption of THz radiation by free carriers and optical phonons, the spectrum of total mode loss of THz QCL with different thickness of n+-GaAs top contact layer are analyses.