卷 53, 编号 1 (2019)

The effect of doping with iron (thermal diffusion from a surface) on the luminescence of zinc-selenide single crystals in the wavelength range 0.44–0.72 μm and on the spatial distribution of luminescence centers are studied. By means of two-photon confocal microscopy, planar and volume maps of edge (exciton) and impurity–defect luminescence in the above-indicated spectral range are obtained for both doped and undoped crystals. It is shown that crystal regions containing a high iron concentration exhibit low-intensity luminescence in this range. It is found that, in the process of diffusion, several types of impurity–defect centers distributed in a complex way within the crystal bulk are formed. The nature of these centers is discussed.

The regularities governing the surface modification of silicon crystals during microwave-plasma microprocessing in different chemically active gaseous media are investigated. This modification is shown to be caused by the formation of built-in surface potentials, which, depending on the semiconductor electrical-conductivity type, differently affect the field-emission properties and surface electron transport in devices based on them.

The relation between the geometry of the metric space of the thin-film TiAlNiAu metallic system surface and the geometry of the functional space of the sheet resistances R_sq of this system is established. Based on the results obtained, the lateral size effect observed in the local approximation is described, which manifests itself in the dependence of the sheet resistance R_sq of a TiAlNiAu metallic film on its lateral (in the (x, y) plane) linear sizes. The dependence of the R_sq value on the linear sizes is shown to be determined by the fractal geometry of the forming dendrites, specifically, by the power dependence of a variation in the linear sizes on the fractal dimension D_f. The obtained regularity is of great practical importance for accurate calculation of the R_sq values ​​of thin-film metal systems in designing discrete devices and integrated circuits and for controlling the technological processes of fabricating thin metallic films and systems based on them at the micrometer and nanometer scales.

A simple numerical method for processing the data of the high-frequency capacitance–voltage characteristics of metal–insulator–semiconductor structures is proposed. The approach is based on analyzing the experimental characteristics near the flat-band states, where the charge exchange of surface localized electron states is of little importance compared with changes in the near-boundary charged layer in the semiconductor. The developed technique makes it possible, first, to find the necessary parameters of the semiconductor and insulating layer and, second, to obtain the experimental field dependences of the energy-band bending in the semiconductor and the total concentration of the built-in charge, the charge of boundary states and minority charge carriers at the semiconductor–insulator interface in the range from the flat bands to deep depletion. The technique is well applicable to structures with an ultra-thin insulating layer. On n-Si-based metal–oxide–semiconductor samples with an oxide thickness of 39 Å, experimental approbation of the proposed approach is carried out. The accuracy of the obtained results is 2–3%.

The goal of this work is to study the processes of self-organization in tetraphenylporphyrin (H₂TPP) films made by condensation under various conditions. Experimental studies of the spectral characteristics of H₂TPP thin films obtained by the liquid method from a H₂TPP toluene solution and by vacuum deposition on different substrates are carried out. It is shown that the structure of the H₂TPP samples changes depending on the technique of synthesis on different substrates, which shows itself in changes (“red” shift) in the photoluminescence and absorption spectra. The changes are caused by a different degree of crystallinity depending on the homogeneity of the surface of the substrates and their temperature.

The recombination activity of intragrain defects in multicrystalline silicon is investigated by the electron or laser beam induced current methods. The interrelation of the grain orientation with the character of the distribution of intragrain defects (dislocations and impurity inclusions) and their recombination activity is revealed. The defect grain structure is investigated using various etching procedures to reveal the defects. It is shown that the defect density and distribution in the grains depend on their orientation relative the growth axis. Therefore, it is intragrain defects and impurities that are to a large degree responsible for degradation of the nonequilibrium carrier lifetime when compared with grain boundaries.

Integrated heterostructures exhibiting a nanocolumnar morphology of the In_xGa_{1 –x}N film are grown on a single-crystal silicon substrate (c-Si(111)) and a substrate with a nanoporous buffer sublayer (por-Si) by molecular-beam epitaxy with the plasma activation of nitrogen. Using a complex of spectroscopic methods of analysis, it is shown that the growth of In_xGa_{1 –x}N nanocolumns on the por-Si buffer layer offer a number of advantages over growth on the c-Si substrate. Raman and ultraviolet spectroscopy data support the inference about the growth of a nanocolumn structure and agree with the previously obtained X-ray diffraction (XRD) data indicative of the strained, unrelaxed state of the In_xGa_{1 –x}N layer. The growth of In_xGa_{1 –x}N nanocolumns on the por-Si layer positively influences the optical properties of the heterostructures. At the same half-width of the emission line in the photoluminescence spectrum, the emission intensity for the heterostructure sample grown on the por-Si buffer layer is ~25% higher than the emission intensity for the film grown on the c-Si substrate.

For a brick-wall-like lattice topologically equivalent to the graphene lattice, a simple structural model of a zigzag edge decorated with particles is constructed. Analytical expressions for the energy band spectrum, densities of states, and occupation numbers of the graphene–particles system are derived for a system in the free state and for a system formed on a metal substrate.

The conduction characteristics of the inversion channel of Si-transistor structures after the ionic polarization and depolarization of samples are measured in (0–5)-T transverse magnetic fields at temperatures from 100 to 200 K. After ionic polarization in a strong electric field at 420 K, no less than 6 × 10¹³ cm^–2 ions flowed through the oxide. The previously found tenfold increase in the conductivity in the source–drain circuit after the polarization of insulating layers is explained by the formation of a new electron transport path along the surface impurity band, related to delocalized D^– states; these states are generated by neutralized ions located in the insulating layer at its interface with the semiconductor.

The simulation of β-voltaic power cells consisting of a combined β-source and a converter was performed. The TiT₂ compound containing the radioactive tritium isotope was selected as the source. As the converter, structures based on semiconductor materials, most commonly used in developing power cells, i.e., Si, SiC, GaAs, were considered. Using the Monte Carlo method, the main source parameters were calculated, in particular, the maximum achievable short-circuit current was estimated.

A sequence of inhomogeneous differential equations for reconstructing the derivative of the nonlinear current–voltage characteristic is studied. The right-hand side of these equations is the experimentally determined dependence of the first-harmonic voltage on direct current. Such voltage arises, e.g., at the output of a nonlinear semiconductor structure simultaneously exposed to alternating and direct current. Based on numerical solutions of differential equations, the developed technique is applied to reconstruct the derivative of the current–voltage characteristic of two antiparallel connected p–n junctions.

The fundamental aspects of the electrochemical etching of lightly doped n-Si under backside illumination conditions are studied in a solution with a low HF concentration and a high concentration of hydrogen peroxide. The data obtained are compared with those for a control electrolyte containing no H₂O₂. The morphology of the self-organized macropores, their growth rate, porosity, effective valence, and the amount of dissolved silicon are examined in relation to the applied voltage. The anodization kinetics at low and high bias voltages is analyzed. It is found that, under the same illumination, the initial photocurrent in the peroxide electrolyte is approximately twice lower than in the aqueous electrolyte, which makes it possible to state that the quantum efficiency of the photocurrent is lower. As, however, the etching duration is made longer, the current in the peroxide electrolyte strongly increases to become higher than that in the control electrolyte based on H₂O. It is found that, in the presence of H₂O₂, the depthwise growth rate of the macropores increases by more than a factor of 2, and the porosity decreases. The vertical macropore channels have a diameter smaller than that for macropores formed in the aqueous electrolyte and their walls are poorly passivated, which causes branching and the formation of secondary mesopores, the number of which grows with increasing voltage. The effective valence of silicon dissolution in the presence of H₂O₂ decreases to less than 2. The results are interpreted in terms of the Gerischer and Kolasinski models.

An ellipsometric procedure developed for noncontact in situ measurement of the CdTe buffer-layer temperature is presented. The procedure is based on the temperature dependence of the energy position of CdTe critical points and is intended for determining the initial temperature of the growth surface before epitaxy of the cadmium–mercury–telluride compound. An express method for determining the position of critical points by the spectra of ellipsometric parameter Ψ is proposed. A series of calibrated experiments is performed. They result in determination of the temperature dependences of the position of critical points. Estimations and the experiment show that the temperature-measurement accuracy is ±3°C.