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We have demonstrated that SiC mesastructures with gently sloping sidewalls form with the help of selective reactive ion etching (RIE) of silicon carbide through a photoresist mask (slanted walls are formed during simultaneous etching of SiC and the resistive mask with the edge in the shape of a sharp wedge). A simple geometrical model of etching predicts that the resultant slope of the mesastructure wall must be specified by two parameters, i.e., initial angle of the resistive wedge and the selectivity of SiC etching relative to the photoresist (ratio of etching rates of SiC and photoresist). For experiments, we used polished 4H–SiC wafers with the (0001) orientation. Photoresist regions with an edge angle of 22° were deposited using photolithography onto the Si side of the wafers. Then etching of mesastructures was performed in nitrogen trifluoride in a setup with an inductively coupled plasma. We selected RIE parameters ensuring SiC and photoresist etching with rates of 55 and 160 nm/min, respectively (etching selectivity was 1 : 3). The SiC mesastructures formed by etching have a height of 3.2 μm and gently sloping sidewalls with a slope of about 8°. This technology can be used for preparing high-voltage SiC devices with a straight bevel.

The prospects for the protection of high-voltage 4H-SiC-devices from edge breakdown via the formation of mesa structures with inclined walls (negative beveling) are considered. Numerical simulation of the spatial electric-field distribution in high-voltage (~1500V) reverse-biased mesa-epitaxial p+–p–n0–n+ 4H-SiC diodes is performed. It is shown that negative beveling with small angles of less than 10° from the plane of the p–n0 junction makes it possible to reduce severalfold the surface edge electric field as compared to that in the bulk. A combined protection method is suggested as the edge-termination technique for 4H-SiC diodes with a p+–n0–n+ structure, Schottky diodes with an n0 blocking base, and bipolar n+–p–n0 transistors via the implantation of boron along with negative beveling. The possibility of fabricating mesa structures with inclined walls via the photolithography and dry etching of silicon carbide is briefly discussed.

Methods of micro-profiling of 4H-SiC are described: formation of mesa structures with inclined walls (off-vertical wall inclination angle exceeding 45°) by reactive ion etching; etching of mesa structures with a flat bottom and inclined walls (off-vertical wall inclination angle being smaller than 45°) by ion-beam and reactive ion plasma etching. The application of etching methods in the fabrication technology of 4H-SiC-based mesa-epitaxial field-effect transistors with a Schottky gate is demonstrated.

The results of a study of multilayer photodiodes based on InAs1- x Sb x solid solutions (0.3 < x λ 0.1 ≈ 11 μm at room temperature are presented. The current-voltage and spectral characteristics of photosensitivity and electroluminescence were analyzed in the temperature range of 80 ÷ 300 K. Experimental samples of photodetectors are characterized by a quantum efficiency of 0.23 at 150 K and a diffusion mechanism of current flow at least in the 200-300 K range. The detectivity of the immersion lens PD at the maximum has values of at least D*8 µm = 8·108 and D* 5.5 µm = 1010 cm·Hz1/2W-1 at 300 and 150 K, respectively.

Narrow gap heterostructures consisting of two double heterostructures (N-InAsSbP/n-InAs/P-InAsSbP and P-InAsSbP/n-InAs0.9Sb0.1/N-InAsSbP) grown sequentially onto a n+-InAs substrate and further processed into a two-color photodiode with individual sensing operation at 3.3 and 4 have been studied. Presented and discussed are the photodiode construction details, I-V characteristics as well as sensitivity and detectivity spectra measured at room temperature.

We present the results of optimization of the design and molecular beam epitaxy (MBE) growth technology of N-AlGaAs:Si/n +-GaAs:Si/p +-GaAs:Be/P-AlGaAs:Be heterostructures for tunnel diodes (TDs). The achieved maximum peak current density level (J p = 513 A/cm2) allows these TDs to be used for cascade connections both in multijunction solar cells and in structures of tunnel-coupled laser diodes. The initial region of the J–U curve of TDs exhibits nonlinearity that is explained by a residual potential barrier left in the p +–P–p + isotype heterojunction (confining the active region of TD) as a result of non-optimum doping of Al0.4Ga0.6As alloy.

A correlation between the main parameter of a solar cell, the conversion efficiency, and its dark I–V characteristic is investigated. A formula is derived that expresses an increment (decrement) of the efficiency through a decrement (increment) of the current measured at a certain voltage (here at 2.4 V). Relationships are deduced based on which six methods for passivating the sidewalls of triple-junction InGaP/GaAs/Ge heterostructures grown by metal-organic vapor-phase epitaxy are tested to see how they influence the dark I–V characteristic. The influence of different factors, such as post-growth annealing, damaging radiation, etc., on the solar cell efficiency can be estimated by taking the dark I–V characteristic.

A computational model is developed for the evaluation of the kinetics of wear and durability of plain bearings taking into account the presence of small out-of-roundness of the contours of their components operating in contact. By using the developed cumulative model, we study the schemes of plain bearings with different lobing of the shaft and the bush. It is shown that the degree of wear of the bush of a bearing increases in the case of lobing of one or both elements. At the same time, the degree of the wear of the shaft decreases. More complex types of lobing of the contours clearly lead to strong changes in the degree of wear.

Characteristics of GaAs photodiodes have been studied before and after the chemical nitridation of their surface in hydrazine sulfide solutions, which leads to substitution of surface As atoms with N atoms to give a GaN monolayer. The resulting nitride coatings hinder the oxidation of GaAs in air and provide a decrease in the density of surface states involved in recombination processes. The device characteristics improved by nitridation are preserved during a long time.