Home – Home – Jornals – Avtometriya 2019 number 5

Ge layers heavily doped by a donor impurity are formed by implanting a p-Ge single crystal by two-charge antimony ions (Sb⁺⁺) with the energy E = 80 keV and the dosage Phi = 10¹⁶ cm^{- 2} with subsequent pulsed annealing of the implanted Ge:Sb layer by powerful ion beams (C⁺, H⁺) of nanosecond duration in a liquid phase. The surface morphology and depth profiles of Sb, the crystalline structure of the layer, the concentration of electrically active atoms, and photoluminescence of the Ge:Sb layers are investigated. The data on the Sb depth distribution are compared with the computer simulation results and show good agreement. The obtained results indicate that a high degree of activation of the implanted mixture of Sb (up to 100 %) and an increase in the direct-gap photoluminescence in the heavily doped layer for 300 K with a peak at 0.77 eV

A method for forming p-n-diode based silicon electro-optic modulators using local oxidation is tested. It is shown that the local oxidation of silicon allows forming a waveguide crest shaped as a smoothed trapezoid, in contrast to the classical technique of creating a waveguide crest by plasma-chemical etching. The main advantages of the approach used are described: controllability and reproducibility of critical structural parameters of the modulators (width and height of the waveguide crest), low surface roughness, and the possibility of using approaches to forming a modulating p-n-diode of combined structure in a ridged waveguide, which is standard for planar technologies.

Two types of mirror structures with saturable absorption are under consideration: monolithic mirrors grown from semiconductor materials and mirrors with a dielectric reflector, with quantum well containing semiconductor structures transferred to the dielectric. Both types of mirrors manifest high reflectivity in the near IR range of the spectrum: the "beam table" width is about 100 nm for semiconductor reflectors and more than 200 nm for dielectric reflectors. It is shown that a maximum depth of absorption modulation from 1 to 40 % is possible. The recovery time of the saturating absorber (2 ps) makes these mirrors significantly fit for using in lasers with a pulse repetition frequency of 1 GHz

The structure and photoluminescence of synthesized perovskite crystals CH³NH³PbI³ (lead triiodide methylammonium) are investigated in a wide temperature range. As temperature rises to 130-140 K, there is a transition from a orthorhombic to tetragonal crystal lattice with a change in the band gap. An increase in the stationary photoluminescence intensity at room temperature under the influence of exciting radiation is revealed. A model explaining the observed growth of photoluminescence is proposed.

This paper presents the results of numerical simulation for 43m class crystals and experimental results for azimuthal angular dependences of polarization components of a signal of a second-harmonic reflected from GaAs substrates with (013) orientation, CdTe/ZnTe/GaAs buffer layers, and Cd_xHg_1-xTe/CdTe/ZnTe/GaAs structures, sequentially grown on these substrates with normal incidence of laser radiation on the sample and azimuthal rotation of its polarization plane. It is revealed from investigating the (013)GaAs substrates and CdTe/ZnTe/GaAs buffer layers that deviations from the base cut (013) relative to angles turn out to be 1-3 in the GaAs substrates and up to 8 in the CdTe/ZnTe/GaAs buffer layers. The observed asymmetry of the minima of angular experimental dependences of the second-harmonic signal in the GaAs substrates is related to stresses. It is assumed on the basis of the experimental data that the tensor components of nonlinear susceptibility of the crystalline structure Cd_xHg_1-xTe significantly exceed similar tensor components in CdTe and GaAs in value

Within the framework of ensuring conditions for the normal operation of photoreceiving diode matrices, the influence of the step profile of a composition on the formation of inversion in cadmium - mercury - tellurium (CMT) films under the action of an embedded charge Qi of an insulating dielectric is studied. The problem of the maximum permissible value of Qi, which does not yet form inversion in the system, is analyzed by varying the system parameters: the values of rupture of the zone edges for charge carriers in the CMT, the thickness of the broadband surface CMT layer, temperature, and the doping level of the two-layer CMT film

Waveguide microstructures based on strained silicon with the use of carbonitride and silicon nitride films as cladding layers are created. A plasma-enhanced chemical vapor deposition technique is developed, which allows obtaining high values of intrinsic mechanical stresses (about 700 MPa). The strained waveguide structures are characterized by micro-Raman spectrography during a scanning procedure. It is demonstrated that deposition of carbonitride and silicon nitride films induces compressive stresses in the silicon waveguide, which is proved by the shift of the maximum of the main peak of scattering on LO-phonons of silicon toward higher wave numbers. The compressive stresses in the silicon waveguide clad with silicon nitride and carbonitride layers are estimated as 350 and 250 MPa, respectively, which is sufficient for the emergence of nonlinear optical properties of silicon (Pockels effect)

Terahertz emission spectra of the surface of silicon crystals with different types of conductivity upon excitation by femtosecond laser pulses at various temperatures were experimentally recorded. Observed features in the terahertz spectra of the a silicon surface correspond to the energy structure of the impurity centers determining the type of conductivity of the sample. Comparison is made with the results obtained in the case of deposition of gold nanoparticles on the semiconductor surface. The spectral features of the surface with the deposed nanoparticles are discussed using the terahertz re-emission mechanism in two-phonon absorption

This paper considers mechanophysical methods (shear under pressure and explosive loading) developed for producing high-density optical nanoceramics based on some oxide magnetic semiconductors and their optical properties. Advantages of the techniques are the ease of implementation, a combination nano grinding and compaction of the material in a single process, obtaining high-density (99 %) stable materials, and the absence of external impurity. It is shown that copper oxide nanoceramics can be used as solar energy absorber and iron-yttrium garnet nanoceramics as an optical element in electromagnetic radiation modulators.

The theory of coherent photon-stimulated electron tunneling through a one-dimensional smooth barrier was successfully used to model the results of measuring the terahertz photoconductivity of a tunnel point contact in a two-dimensional electron gas. For this barrier in a deeper tunnel mode, photon steps in the dependence of the tunneling coefficient on the initial electron energy were found. Their position is determined by the energy of the terahertz photon

A local spectral analysis of multicomponent semiconductor nanostructures was performed based on the giant Raman scattering by semiconductor nanostructures on the surface of an array of Au nanoclusters near the metallized needle of an atomic force microscope. In the gap between the metal nanoclusters and the needle, where a semiconductor nanostructure is located, there is a strong increase in the local electric field (hot spot), resulting in a dramatic amplification of the Raman scattering signal. Unprecedented amplification of the Raman scattering signal by two-dimensional (over 10⁸ for MoS₂) and zero-dimensional (10⁶ for CdSe nanocrystals) semiconductor nanostructures was achieved. The use of the method for mapping the Raman scattering of a multicomponent system of MoS₂ and CdSe made it possible to identify components with a spatial resolution far exceeding the diffraction limit

A method is proposed for determining the orientation of phospholipide molecules in planar structures from spectra of non-polarized Raman scattering. The method is based on the sensitivity of the intensity of lines of Raman scattering on oscillations of CH₂ groups to the orientation of phospholipide molecules. The validity of the method is illustrated on a planar specimen of a saturated phospholipide prepared by drying from a solution. It is demonstrated that it is convenient to use the method of principal components to analyze the spatial distribution of molecule orientations in the specimen

The paper presents the results of calculation and growth of AlGaN/AlN heteroepitaxial structures with Bragg mirrors for the blue-green spectral range corresponding to the maximum broadband luminescence of the AlGaN:Si layers by molecular beam epitaxy from ammonia. Structures with an active AlGaN: Si region located on one lower Bragg mirror for a wavelength of 510 nm and between two Bragg mirrors for a wavelength of 510 nm were grown. For both heteroepitaxial structures, selection of the radiation of the active layer in the given spectral range by the lower Bragg mirrors was demonstrated. It is shown that a large total thickness of the heterostructure with two Bragg mirrors leads to cracks and macroscopic defects on the surface of the heteroepitaxial structure

The absorption spectral characteristics of silicon dioxide films in the IR range (λ =8-14 mu m) were studied to determine the optimal absorber thickness in the matrix structure of Golay microcells in order to design highly sensitive IR radiation detectors. It is shown that the absorption spectrum of SiO₂ films deposited by electron-beam evaporation has a multipeak structure in the thickness range up to 2 mkm and differs from the known absorption spectra of bulk silicon dioxide, which is apparently due to rearrangements in the film stoichiometry at the initial stages of film formation. Experiments have shown that the integrated absorption in deposited films in a given spectral range is close to a linear dependence on thickness and an order of magnitude smaller than the value obtained by calculation based on literature data for bulk SiO₂

This paper presents the results of the development and testing of a complex for studying the operating modes of CCD sensors. The purpose of the study is to verify the performance of these matrices as part of a gated-viewing system without using an image intensifier or other external high-speed gate in its design. The complex allows one to control a commercial CCD sensor by an undocumented method using signals of arbitrary shape, synchronize its operation with a laser emitter, receive and digitally process an image and transfer it to external devices. Conducted experiments on various CCD sensors have shown that the possibility of designing a gated-viewing surveillance system based on an interline transfer CCD sensor without using an image intensifier and the possibility of practical application of such a system

Charge carrier diffusion is simulated by the Monte Carlo method in a photosensitive film of cadmium - mercury - tellurium (CMT) based infrared photodetectors for determining the spatial resolution of these photodetectors. Calculation results for matrix and linear photodetectors with differently designed matrix photoelements, including configurations with isolating diodes, are given. The calculated data are compared with experimentally measured resolutions of real photodetectors

This paper presents finite-element mathematical models for the real and simplified telescope lenses of the Lira-B space experiment. The results of calculation of the mechanics of the lens upon exposure to various external loads, both static and dynamic, are given. The calculations were performed using the ANSYS software package. Three methods for determining the characteristics of lightweight structures of the lens parts, two of which are used in the calculations, are described. Comparison of the results obtained using the real and simplified (reduced) models indicates that the simplified model can be used for initial estimates. Moreover, using this model with reduced characteristics, it is easier to develop and generate a finite element mesh, and it requires significantly shorter computational time