Home – Home – Jornals – Avtometriya 2021 number 5

The results of the development of vertical-cavity surface emitting lasers based on Al_xGa_1-xAs and In_yGa_1-yAs solid solutions are presented. Developed lasers demonstrate stable single-mode operation at a wavelength of 794.9 nm and 894.6 nm, which offers the prospects of their applications in miniature quantum frequency standards operating at the transition 5S_1/2→5P_1/2 of ⁸⁷Rb and ¹³³Cs atoms.

The mechanisms of surface transformation during annealing of epi-ready InP (001) substrates in a flux of arsenic molecules have been studied in situ by reflection high-energy electron diffraction. The effect of the annealing temperature and the arsenic flux on the processes of removing oxides from the InP surface, which occur as a result of thermal decomposition and chemical interaction of oxides with arsenic, has been studied.

The analysis of the processes of generation of the second harmonic in the layers of CdTe, CdxHg_1-xTe and the substrate from GaAs heterostructure Cd_xHg_1-xTe/CdTe/ZnTe/GaAs orientation (013) is carried out. Measurements of the azimuthal dependence of the signals of the second harmonic in comparison with the calculated data obtained during the numerical modeling of the ideal crystal for a given orientation near the cut (013) were carried out. It is shown that the substrate and epitaxial layers after cultivation have a reversal of the orientation plane, which was for substrates of GaAs +8 and -3 angular degrees from the ideal plane (013), for layers of heterostructures - up to 8 angular degrees from the orientation of the substrate, which has a weak dependence on the composition in thickness. The observed reversals of the orientation plane depend on the discrepancy between the parameters of the lattice of the conjugated materials of the heterostucture Cd_xHg_1-xTe /CdTe/ZnTe/GaAs. The recorded increase in noise with the minimums of azimuthal dependence of the second harmonic signal in the layers of Cd_xHg_1-xTe is due to the presence of disoriented microsicts.

The action of quantum wells design and specific features of their manufacturing technology on the performance and maximum modulation depth of optical shutters based on quantum wells A₃B₅ predestinated for mode locking of NIR lasers is analyzed.

The problem of in situ temperature control during the growth of epitaxial layers of CdHgTe by molecular beam epitaxy is considered. Various approaches to solving the problem using spectroscopic ellipsometry are proposed. They are based on the temperature dependence of the optical constants spectra of the CdTe buffer layer and the growing CdHgTe layer. The results of experimental testing of these methods are presented, which show that the temperature measurement accuracy is several degrees, and the sensitivity reaches fractions of a degree. At the stage of stationary growth, it is possible to determine the change not only in temperature, but also in the composition of the growing layer from the ellipsometric spectra.

The issues related to the development and manufacturing single photon detector based on single-photon avalanche photodiodes (SPAD) InP/InGaAs/InP, operating in Geiger mode on telecommunications wavelength 1550 nm are discussed. A description of the SPAD design is given. The method of obtaining the InP/InGaAs/InP heterostructure by molecular-beam epitaxy, methods of manufacturing SPAD chip by planar technology, features of selective doping with zinc p-regions in the InP layer and developed electronic schemes for measurement main parameters of SPAD are described. Preliminary results of measurements SPAD parameters are presented.

The antireflection properties of coatings composed of subwavelength-sized dielectric SiGe particles grown on Si(100) substrates using the dewetting phenomenon are studied. The average particle size was set by the amount of deposited Ge and varied in the range from 0.2 to 1.4 μm. The excitation of magnetic and electric resonances in the SiGe particles led to a decrease in reflection by approximately 60%, depending on the average particle size, in comparison with the reflection of the Si surface not covered with particles. The broad particle size distribution provided the antireflection properties over a wide spectral range, in which small particles produced a stronger antireflection effect than large particles. Numerical simulation has shown that for particles on a substrate, the efficiency of excitation of magnetic and electric resonances strongly depends on the ratio of the height of the particles to the size at their base.

The use of the vacuum photodiode with two semiconductor electrodes for studying the multialkali photocathode (MP) photoemission properties was demonstrated in this work. The photoluminescence and quantum efficiency spectra were studied; the high-resolution energy distribution curves for the MP were obtained for the first time. The measurements were performed under illumination of the MP in the spectral range of 400-950 nm and the temperature range of 90-300 K. Using the data obtained the conclusion, that the MP is a photocathode with effective negative electron affinity, was made. The properties of the solar element based on the vacuum photodiode were studied.

Theoretical relations that optimize the design of the microbolometric elements of the FPA providing an improvement in its operating speed are presented. The requirements for the parameters of the elements and the materials used for its manufacture are formulated, which provide a fundamental opportunity to minimize the thermal relaxation time of a bolometric sensor in order to increase the frame frequency of the FPA. The results of their modeling are presented, which make it possible to optimize the design and its implementation using modern technological processes for the formation of microbolometric elements with high operating speed, taking into account the requirements of specific applications.

The design of microcavity for single quantum dot based emitters has been developed. The microcavity consists of semiconductor distributed Bragg reflector and microlens, fabricated by selective oxidation of gradient Al_XGa_1-XAs layer. The microcavity demonstrates high level of external quantum efficiency up to 70%. This microcavity can be used in the development of a single quantum dot based single photon emitters or emitters of entangled photon pairs.

Photoluminescence of structures with multiple GaN/AlN quantum wells grown by molecular beam epitaxy has been investigated. Calculated dependence of the quantum well photoluminescence band peak energy on the thickness of the GaN layer has been compared with experiment for various ratios of the thicknesses of the GaN and AlN layers. The thicknesses of the GaN and AlN layers were determined by transmission electron microscopy. The calculations of the photoluminescence band peak energy were carried out in the 6-band kp-approximation taking into account spontaneous and piezoelectric polarizations. According to the calculation results, the slope of the dependence of the emission energy on the GaN layer thickness decreases with increase in the ratio of the GaN layer thickness to the AlN layer thickness, in accordance with decrease in the electric field in the GaN layer. In quantum wells of sufficiently large thickness the observed photoluminescence band peak energy is higher than the calculation result for undoped structures due to unintentional doping of the quantum wells, which leads to screening of the built-in electric field.

A comprehensive study of monolayers of molybdenum disulfide MoS₂, formed on a silicon substrate using Raman scattering (RS), photoluminescence (PL), was carried out in comparison with the data of atomic force microscopy (AFM). Maps of the distribution of the Raman scattering intensity by optical phonons and exciton PL from monolayer MoS2 films were constructed. The dependences of the frequencies of the fundamental vibrational modes of MoS₂ (A_1g and E_2g) on the thickness of monolayer coatings were obtained. An enhancement of the Raman mode of the optical phonon of silicon by a bilayer of molybdenum disulfide was found. A hypothesis on the interference enhancement of Raman scattering of light by phonon modes of silicon is proposed.

This article is dedicated to the famous physicist, founder of the School of acousto-electronics and acousto-optics, corresponding member of the Russian Academy of Sciences, Sergey Vasilyevich Bogdanov in connection with the centenary of his birth (2.08.1921-14.02.2017).

Fundamental research of basic creating mosaic focal plane arrays (MFPAs) allowed to optimize the prototype of mosaic technology with decreasing "blind zones". At the same time, minimal damage areas are provided at the edges of the crystals after separating the wafers with the achievement of minimum gaps between crystals of adjacent submodules up to a value of no more than 2-3 microns for different determining materials. The parameters of infrared MFPAs are investigated depending on the wavelength of the maximum spectral characteristic of the photosensitivity of multilayer structures with quantum wells, on the pitch of quantum well photodetectors and on the format of submodules. In a series of the proposed variants of technological prototypes, the "blind zones" of the MFPA are optically overlapped and the ultimate, 100%, image-conversion efficiency is provided. The mosaic technology is one of the fundamental principles of achieving ultra-high dimension of the MFPAs with maximum image-conversion efficiency.

The paper proposes algorithms that allow to increase the efficiency of parallel programs execution on high-performance computer systems, in particular, when solving problems of modeling physical processes. The developed algorithms are focused on reducing the execution time of collective operations for computer systems with SMP/NUMA node architecture in standard MPI libraries. The developed read-write blocking algorithms increase the efficiency of synchronization of access to shared memory, relative to the algorithms used in the Open PMIx library.