A periodic semiconductor structure is considered, consisting of tunnel-uncoupled quantum wires (QW) based on InSb containing impurity centers. The uniform magnetic field is directed along the QW axis. For the case of light polarization transverse with respect to the QW axis in the framework of the dipole approximation, in the effective mass approximation, an analytical expression for the impurity absorption coefficient of light is obtained taking into account the dispersion of the QW radius described by the Gauss function. It is shown that on the spectral curve constructed in the Maple program, for given parameters of the QW and the semiconductor structure, there is a sequence of resonant maxima with a doublet structure. The cyclotron frequency determines the distance between the maxima in the doublet, and the frequency of the doublets on the spectral curve is determined by the hybrid frequency. With an increase in the magnetic field, the dynamics of the edge of the impurity absorption band is observed, which can be used to create detectors of optical radiation in a wide range of wavelengths and will make it possible to identify such semiconductor structures. It is also possible to obtain valuable information about the parameters of the QW and the band structure of the semiconductor from the spectral curve
Keywords: impurity absorption coefficient, quantum wire, low-dimensional semiconductor structures, impurity center
A semiconductor quantum wire (QW) containing an impurity center described in the framework of a hydrogen-like model is considered. The possibility of using InSb QW in photodetectors of infrared optical radiation is discussed. The QW is modeled as a geometrically symmetric cylinder, on the axis of which an impurity center is located at an arbitrary point, with which the origin of the cylindrical coordinate system is associated, in which calculations are performed. It is assumed that the magnetic length is much smaller than the effective Bohr radius - the case of a strong magnetic field. This approximation made it possible to make the impurity potential effectively one-dimensional and obtain analytically accurate calculation results. In the effective mass approximation, in the dipole approximation, an expression is obtained for the matrix elements of the optical transitions of an electron from the impurity ground state to the size-quantized QW states for the case of transverse light polarization and the Kane dispersion law of charge carriers.
Keywords: matrix elements of optical transitions, effective mass method, quantum wire, dipole approximation, size-quantized states
In this work, a theoretical determination of the transfer coefficient of millimeter-wave mixers based on resonant tunneling diodes is carried out. The analysis of the conditions for optimizing the transmission coefficient of microwave mixers using resonant tunneling diodes as nonlinear elements is carried out. The optimal constant voltage is determined, at which the amplitude of the local oscillator, required to obtain the maximum transfer coefficient of the mixer, will have the smallest value, and the coefficient itself will be the largest.
Keywords: gain, mixer, millimeter wave, frequency conversion, local oscillator amplitude, modified Bessel functions, stability factor, resonant frequency, bandwidth
The electrophysical and mechanical properties of a piezoceramic material based on CTS are investigated. A number of features in the behavior of the electrophysical properties of the material in the temperature range located significantly below the low-frequency (1 kHz) maximum of the dielectric constant T_m = 160℃ have been revealed. The obtained results indicate the proximity of the studied material to ferroelectric relaxors, in particular, the low coercive field E_c~5 kVcmcm, the significant dependence of T_m on the frequency and amplitude of the measuring field, as well as the behavior of the velocity of longitudinal ultrasonic waves in this ceramic. It is shown that the elastic properties of this material are very close to ferroelectric relaxors, having a high malleability in a very wide temperature range. At the same time, the squareness of the polarization loops at relatively low temperatures indicates the manifestation of the classical properties of the ferroelectric during the polarization switching processes, and not the "freezing" processes characteristic of ferroelectric relaxors. From the results obtained, it can be established that this composition will be promising for use in the actuators of adaptive optics systems and precision positioning devices due to the high values of piezomodules.
Keywords: PZT system, ferroalloy ceramics, dispersion, polarization, elastic properties, blurred phase transitions, curie temperature, depolarization temperature, ferroelectric relaxor, rhombohedral phase, tetragonal phase
This article presents one of the methods for analyzing the chirality coefficient of a medium depending on such parameters as concentration n, frequency f, dielectric constants of both the container material, the medium itself, and left- and right-handed spirals distributed in this material. As a result of this work, the frequency characteristics of the chirality coefficient were obtained at various concentrations of the container trace elements.
Keywords: chiral medium, Telledzhene element, chirality coefficient, dielectric constant of the medium, magnetic permeability of the medium, spiral structure, metamaterial substrate, bulk concentration, metamaterial, spiral inclusions
The use of high-power thermistors as part of the control gear facilitates a smooth start-up of powerful motors with simultaneous temperature control. When calculating the starting processes, there are a number of limitations on which the nature of starting electric motors with the use of thermistor rheostats depends. The calculated relations describing the mathematical model of the influence of the temperature of overheating of semiconductor thermistors on the process of starting motors with a start-up rheostat are presented in the form of graphic dependences. As a result of modeling the layout of thermistor rheostats, it was determined that it is necessary to pay special attention to the material heating temperature.
Keywords: semiconductor thermistor, starting rheostat, boundary conditions, heating, specific heat, induction motor, starting current, overheating temperature
The main results of studies of the anodic behavior and chemical composition of the surface layer of the aluminum film before and after implantation of silicon ions (20 keV), conducted using the method of measuring potentiostatic polarization curves, are presented. The decrease in the anode polarization currents and the expansion of the passivation region depending on the dose of the introduced ions, due to the formation of oxide compounds with the implanted silicon impurity, are shown.
Keywords: ion implantation, films, aluminum, polarization curves, potentiostat, anode behavior, auger electron spectra, electrolyte, silicon ions
In this work, R, L, C - parameters of spiral structures with sizes l and S were determined to obtain artificial chiral substrates. This made it possible, given the parameters of the polarizability of the helical structures αij, to use these features to determine the conducting properties of metamaterials. The basic relationships have been determined (for determining the electrophysical parameters of spirals (left- and right-handed) that are included as chiral inclusions in the metamaterial. An algorithm for calculating conducting structures using the proposed equations is proposed.
Keywords: biological liquid medium, dielectric constant, complex dielectric constant, loss tangent, medium conductivity, frequency response, fluctuation, frequency range, biophysical parameter
The article describes the design of the integral micromechanical sensor of linear accelerations of the capacitive type; A construction method is briefly described using the self-assembly operation based on controlled self-organization of mechanically stressed semiconductor GaAs / InAs layers. The design of the capacitive accelerometer was modeled in the CAD system ANSYS, where static and modal analysis were performed. The results of mathematical modeling meet the requirements of modern micromechanical accelerometers, and allow them to be used for the further development of structures of this type. The obtained data can be used in particular for calculating the recommended parameters in the development of methods for designing capacitive sensors of angular velocities and linear accelerations and for developing more accurate models of MEMS structures.
Keywords: MEMS, microelectromechanical system, accelerometer, modeling, design, sensor, sensor, mathematical model
Semiconductor heterostructures in which the spin-orbit interaction is associated with the absence of a center of symmetry that limits the potential of the structure are the basis for future spintronics devices. One of the main methods for investigating into spin properties is the study of optical phenomena in magnetic fields. The article theoretically consider the effect of spin-orbit interaction on absorption in quantum wells, in particular, the intraband magnetic absorption of electromagnetic radiation of linear polarization by a two-dimensional electron gas with Rashba spin-orbit interaction. The coefficient of light absorption by free carriers in the quasi-two-dimensional system was calculated in the second order of perturbation theory. It is assumed that infrared electromagnetic radiation is absorbed in a quasi-two-dimensional system by free carriers, that are scattered by optical, piezoelectric, and acoustic lattice vibrations. The quantum-mechanical motion of an electron in a two-dimensional system in a constant uniform perpendicular magnetic field is described by the Hamiltonian taking into account the Rashba spin-orbit interaction and Zeeman splitting. We calculated the light absorption spectra of 2D electron gas for GaAs / In0.23Ga0.77As lattice structures.
Keywords: Rashba spin-orbit coupling, intraband magnetoabsorption, quasi-two-dimensional electron system, magnetic field, Landau levels, Zeeman splitting, wave functions
The problem of creating semiconductor thermoresistors (PTR) capable of dissipating large amounts of heat is an urgent problem of semiconductor technology. The article presents a brief analysis of the possibilities of using high-power ATGM, the picture of the distribution of thermal fields in the mass of the thermistor under certain boundary and initial conditions. It is shown that when selecting a thermistor material, special attention should be paid to the specific thermal conductivity of the material.
Keywords: High power thermistors, current density, thermal conductivity, energy balance, similarity criteria
This paper contains an analysis of the modeling results of the electrophysical parameters of light-emitting GaInAsSb / GaSb solid solutions. The model takes into account three types of current - drift, thermionic emission and tunneling through potential barriers. In the work, graphs of radiation power versus current strength and current-voltage characteristic (IVC) of the LED device are plotted. Modeling indicators based on the features of the band structure of semiconductor systems have been built. Experimental results were discussed, which showed satisfactory agreement with the data obtained on the basis of calculations.
Keywords: solid solutions, Sim Windows 1,5, radiating structures, currents limited by space charge, electrophysical parameters
The article is devoted to the problem of theoretical research and development of perovskite-based solar cells to optimize their design and increase efficiency. The paper presents a numerical simulation of the transfer and accumulation of charge carriers in the planar p – i – n heterostructure of a solar cell. The simulation is based on a stationary physico-topological model based on the diffusion-drift system of semiconductor equations. The efficiency of solar cells for different perovskite film thickness was obtained. It has been established that the maximum efficiency of the optimized design of a solar cell is about 27% with a perovskite film thickness of 500-700 nm and a defect concentration in it of the order of 1012 cm-3.
Keywords: Numerical simulation, solar cell, perovskite, film thickness, defect concentration, current-voltage characteristic
When modeling the transport of hot carriers in strong electric fields and using various mathematical relationships describing these processes, usually do not take into account inhomogeneities of impurity doping, which affect the field distribution and the density of the output current. In this paper, we calculated the field distribution along the length of the diode chip. In this case, a one-dimensional model and a phenomenological approach to the description of carrier behavior were used. The results obtained allow one to estimate the influence of the inhomogeneity on the operating modes of the Gunn diode and can be used to create models of higher orders.
Keywords: Gunn diode, numerical modeling, heterogeneity doping physical topological model
Numerical modeling of the temperature distribution during heating (annealing) by a pulsed Nd: YAG laser of an amorphous silicon (a-Si) film on the surface of an AZO glass substrate is carried out. The simulation was performed on the basis of a numerical solution of the heat equation in the Matlab program to determine the energy density of the laser radiation necessary for crystallization of the a-Si film. For a wavelength of 1064 nm, it was obtained that the temperature at the surface of the a-Si film reaches a maximum value at a time point of 146 ns with a laser pulse with a Gaussian time-shape. It is shown that for the crystallization of an a-Si film with a thickness of about 800 nm with laser radiation with a nanosecond pulse duration, the optimum energy density is 600-700 mJ / cm2 when the temperature across the thickness of the a-Si film corresponds to 550-1250 ° C.
Keywords: Numerical simulation, laser annealing, temperature distribution, a-Si film, solar cell
In the article, a numerical study of the heat sink with a change in the aggregate state of the oil is carried out. Simulation was carried out in Ansys Fluent CAD for two modes, static - with constant heating of the oil at 340K and dynamic, at which the heating temperature varied with time from 340K to 270K. Heat transfer in the event of a change in the aggregate state of a substance is widely used in cases where it is necessary to achieve the maximum efficiency of heat exchange. In this case, the energy is expended on the phase transition of the substance, for example, to evaporation from the liquid phase. The advantage of the heat-sink design described in this work is a rather high rate of heat transfer, greater resistance to various influences, including mechanical ones, which is primarily ensured by the simplicity of construction, eliminating the drawbacks of classical designs, which are cumbersome (the presence of an external cooling circuit ) and the limited rate of heat transfer.
Keywords: heat dissipation, numerical methods, aggregate state, computational experiment, heat exchange efficiency
In the article, the authors carried out a computer experiment in Ansys Fluent CAD to study the efficiency of a heat sink surface in terms of reducing the temperature of a heat-loaded source. Providing optimal thermal conditions for electronic products is one of the most important problems in the design of radio electronic equipment. Increasing the temperature of electronic products significantly reduces the reliability of their work. The work is devoted to numerical modeling of the heat sink surface efficiency of a pin radiator with an internal heat source. A conclusion is drawn about the ineffectiveness of performing a heat sink pin surface, not the entire surface is equally effective.
Keywords: thermal mode of equipment, pin heat sink, numerical methods, aerodynamic flow
The paper considers methods of taking into account the energy dependence of the effective mass of hot carriers in the volume of semiconductors of the AIIIBV type for three different cases of dispersion. The classical deviation of the dispersion from the quadratic law, the Kane deviation of the dispersion from the quadratic law and the dependence m (W), connected with the two-valley representation of semiconductors of the AIIIBV type, are analyzed. Energy dependences of the normalized effective mass for the main valley, lateral valley, and total energy are calculated, taking into account the intervalley transition and also the energy dependences of the normalized effective mass calculated by the equations. An estimation of the effect of an external electric field on the average carrier energy taking into account different dispersion mechanisms is made.
Keywords: dispersion characteristic, effective mass, quadratic law, Keynes deviation of dispersion, effect of "weighting" of electrons, energy dependencies, heating effects
Piezoceramic frames made of PKP-12 material with porosity up to 50% are made. The effect of the total, open and closed porosity on the properties of porous piezoelements on a given piezoelectric material is studied. Hydrostatic tests of porous piezoelements have been performed to determine the pressure at which irreversible changes occur.
Keywords: piezoceramics, PKP-12, piezocomposites, porous piezoceramics, piezoelectric materials, ferroelectrics, PZT, hydroacoustics, hydrophone
Numerical physical-topological modeling is carried out to optimize the thickness of perovskite solar cells on the basis of the heterostructure TiO2 / CH3CN3PbI3-xClx / Spiro-OMeTAD. The results of the conducted studies showed that the optimum values of the thicknesses of TiO2 and CH3CN3PbI3-xClx heterostructure films, which make it possible to obtain a high coefficient of efficiency of the solar cell, lie in relatively narrow limits. The carried out researches have shown the possibility of effective use of numerical physical-topological modeling for the development of perovskite solar cells, taking into account the features of photogeneration, recombination and transport of charge carriers in real heterostructures.
Keywords: Solar cell, perovskite, titanium dioxide, heterostructure, numerical simulation.
In this work, a study was made of the efficiency of the heat sink surface of a volumetric body with an internal heat source. An electrostatic analog of the distribution of the thermal field is chosen. A model of the convective flow is proposed, under certain initial and boundary conditions, the thermal conductivity of the medium transforming into heat removal. The conclusion is made about the ineffectiveness of the heat-conducting surface in the form of whip, finned and other designs of existing heat sinks, increasing only the mass, technological complexity of manufacture, thermal resistance and temperature of the heat-loaded element.
Keywords: Temperature field, convective heat transfer, effective heat sink area, electrostatic analog, similarity theory
The loops of the dielectric hysteresis of a soft ceramics based on PZT with Curie temperature TC=210℃ are investigated. The studies were carried out at a frequency of 50 Hz in two modes. In the first of them, the field was switched on by 0.07 seconds, in the second - it operated continuously. The amplitude of the field E_m varied from 2.5 to 25 kV / cm and switched stepwise with an interval of 15 minutes. The coercive field EC and the switchable polarization P_m were determined. The switching polarity in the saturation region turns out to be no more, in contrast to BaTiO3 and other materials, but less than the corresponding values obtained with short-term switching.
Keywords: piezoceramics, piezoelectric material, hot pressing, dielectric hysteresis
Theoretical studies of the temperature distribution during laser heating of the TiO2 precursor film on the FTO/glass substrate have been carried out. The simulation was performed on the basis of a numerical solution of the heat equation in the Matlab program to determine the energy density of the laser radiation necessary for crystallization of TiO2. It was shown that on the surface of the TiO2 precursor the temperature reaches a maximum value at a time point of 133 ns with the Gaussian temporal form of the laser pulse. The optimum energy density for crystallization of the TiO2 precursor film with the nanosecond pulse duration is 1.3-1.6 J/cm2, when the film thickness temperature corresponds to 400-500 °C. The obtained results of the simulation are consistent with experimental studies.
Keywords: numerical simulation, laser heating, temperature distribution, TiO2 film, solar cell
In this paper, the temperature distribution from a point source of heat under convective heat transfer is studied. The Navier-Stokes equation describing the steady two-dimensional laminar motion of a fluid is solved numerically. The distribution of the temperature field of a heat-loaded point source is obtained under appropriate boundary conditions, supplemented by the boundary conditions for the flow velocity to equal zero on the paraboloid walls by numerical integration using the control volume method.
Keywords: Radiator protrusion shape, thermal conductivity, thermal apparatus mode, the temperature of the heat source
Nanocrystalline TiO2 films are used as transparent layer n-type conductivity in the perovskite solar cells. The work presents the numerical diffusion-drift modeling of the transport processes and the accumulation of charge carriers in the heterostructure of TiO2 / perovskite / p-type semiconductor. The basis of the simulation put stationary physical and topological model based on drift-diffusion equations and semiconductor system allowing to model perovskite solar cells with a variety of electro-technological and constructive parameters. Obtained photovoltaic solar cell characteristics and plotted the efficiency of the TiO2 film thickness. The optimal thickness of the TiO2 film is 50-100 nm, thereby increasing the perovskite solar cell efficiency.
Keywords: Solar cell, thin film, titanium dioxide, p-i-n structure, numerical modeling