It was found that the synthesis of silicon carbide epitaxial layers on silicon by coordinated substitution of atoms can be accompanied by the formation of silicon carbide nanotubes growing deep into silicon substrates. That is, for the first time discovered a new “top-down” mechanism for the formation of silicon carbide nanotubes.
The features of the formation of porous layers on substrates of low doped silicon of и-type conductivity by anodic etching using illumination are considered. The formation of microporous silicon layer on the walls of macropores was found. It is shown that the illumination modes strongly influence the morphological parameters of the obtained layers. After exposure to alkali, macroporous layers with pore diameters up to 550 nm were obtained, which can be used to create filter layers.
A series of low-voltage thyristor current switches based on (Al)GaAs/GaAs homo- and heterostructures with a volume charge region formed in the lightly doped p-GaAs base layer have been developed. The transient processes characteristics in pulse generation mode of nanosecond duration have been studied. It has been shown that the use of a wide-bandgap barrier based on AlGaAs at the n‑emitter/p-base junction allows reducing the minimum control current amplitude from 30 to 3 mA, and the turn-on delay time can be shortened to 6 ns. For the developed thyristor switches, a minimum transition time of 3.7–3.9 ns was demonstrated when operating in a circuit with a 1 nF capacitive load. In a circuit with a nominal 1 Ω resistive load, the thyristor switches provided a peak current of 17.5 A with a pulse duration of 3.7 ns.
Semi-Dirac crystals with a weak periodic modulation of the energy gap has been considered. The formation of minibands in such crystals has been studied when the latter are placed in a quantizing magnetic field. The width of the formed magnetic minibands has been shown to depend not only on the magnetic field intensity, but also on the band gap of the initial sample in contrast to gap graphene. The effect of this feature on the magneto conductivity of studied material has been investigated.
The influence of AlGaAsP, GaAsP and AlGaAs/GaAsP compensating layers on the optical quality of the active area based on InGaAs/GaAs quantum wells for LEDs emitting at a wavelength of 940 nm has been studied. Heterostructures with multiple quantum wells have been grown by MOVPE technique using various approaches to compensating structural stresses. An increase in photoluminescence intensity by more than 32% was demonstrated when using AlGaAs/GaAsP compensating layers.
Collision cascade density is one of the most important parameters that determine radiation damage accumulation in semiconductors under ion bombardment. We perform calculation of collision cascade parameters formed in β-Ga2O3 by irradiation with 1.3 keV/amu atomic F, P, and molecular PF4 ions using two different methods: the method considering sub-cascade formation, and by calculation an average number of vacancies in spheres of fixed radius. The calculated results are compared with experimental data on damage accumulation in β-Ga2O3 under irradiation with aforementioned ions. It is shown that both methods qualitatively predict the effect of collision cascade density on radiation damage accumulation in gallium oxide. Fractal nature of cascades formed in β-Ga2O3 is established, corresponding fractal dimension is calculated.
In this paper, we propose a method for resonant optical excitation of ortho states of two-electron donors in silicon, direct transitions to which from the ground state are extremely suppressed in case of a weak spin-orbit coupling. Excitation is proposed to be carried out using the points of anti-crossing of ortho and para states under conditions of uniaxial stress of the crystal. In these points the states cannot be unambiguously assigned to any group of states with a certain spin, as a result of which the optical transition becomes allowed. The structure of the energy levels of two-electron impurities is such that the excitation of such state almost unambiguously leads to the population of the underlying ortho-type state, which is expected to be very long-lived in the case of weak spin-orbit coupling. In the present work, theoretical estimates of the cross sections for optical transitions in the vicinity of the level anticrossing point as a function of strain for strong and weak spin-orbit coupling are made.
A quantitative model of the breakdown of MOS-structures with relatively thick (10–100 nm) gate dielectric by the mechanism of anode hydrogen release from interphase boundary Si-SiO2 is proposed. The breakdown delay time is determined by dispersion transport and accumulation of hydrogen ions in the gate dielectric. It is shown that at a high concentration of hydrogen in MOS structures and electric field strength of less than ~10 MV/cm, the model satisfactorily describes breakdown delay times significantly shorter than those expected from the 1/E model. At higher field strengths, the breakdown is described by the anode hole injection model.
It is shown that when using a standard electrochemical profiling recipe that applies intensive illumination by halogen lamp with power up to 250 W of n+/n GaAs structure to generate the holes necessary for etching, the resulting electron distribution profile differs from that set during growth for an electron concentration in the n+-layer > 4 × 1018 cm–3 when using EDTA electrolyte. This difference is due to the appearance and development of etching pits caused by the increase in the degree of defectivity of GaAs layers with increasing concentration of the donor impurity—silicon. To obtain adequate electron distribution profiles in n+/n GaAs structures it is necessary to limit the illumination up to 25 W.
Two-subband magnetotransport of quasi-2D electron gas in GaAs single quantum well with AlAs/GaAs superlattice doping has been studied at T = 4.2 K in magnetic fields B < 2T. It was demonstrated that application of negative gate voltage leads to transformation of studied two-subband electron system into the one-subband system. This transformation is accompanied by appearance of positive magnetoresistance. This behavior has been described by conventional model of classical positive magnetoresistance that takes into account elastic intersubband scattering of electrons. Combined analysis of classical positive magnetoresistance and quantum magneto-intersubband oscillations makes it possible to define the values of transport rates of intrasubband scattering and quantum rate of intersubband scattering.
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