Pleiades Publishing Ltd

A real structure and optical properties of micron porous silicon layers on Si(111) (Sb) substrates were studied by the two-crystal X-ray diffractometry and reflectometry, scanning electron microscopy, and infrared spectroscopy methods in a 4000- to 12000-cm−1 frequency range. The porous silicon layers were formed by the electrochemical etching method at a 50-mA/cm2 current in a hydrofluoric acid/ethanol mixture in a ratio of 1: 1. The structural parameters of the layers are determined, namely, the thickness is 6–66 μm, the average deformation is ≈4.5 × 10−4, and the density is ≈0.72. It is shown that the studied porous layers can be considered uniform only to some extent. The optical transmission spectra were analyzed within the frameworks of the effective medium model and the refractive index n of the substrate was estimated. It is determined that the Si(111) (Sb) substrates have a pronounced transmission band in the spectral range of 1.05–1.5 μm. To restore the dispersion of optical constants from transmission spectra, the procedure, based on the mathematical treatment with regard to real geometric and physical parameters of several transmission spectra by minimizing functional χ 2, was proposed. Possibilities of applying the proposed procedure for determinations of optical characteristics of thin layers and heterostructures are discussed.

In the field-effect transistors based on the wide-band-gap nitride heterostructures, the dielectric layers are in widespread use as one of the main elements in the active regions of the devices and the passivation layers. Stringent requirements are imposed on the dielectrics in terms of the high dielectric capacitance, large band-gap energy, and the coating integrity. Furthermore, the films must withstand high electric fields and have a low surface state density in the dielectric/semiconductor interface. For these purposes, the low temperature films grown by plasma-enhanced chemical vapor deposition, atomic layer deposition (ALD), and plasma-enhanced deposition are usually used as effective coatings. The ALD films of Al2О3, SiNх (Si3N4), SiON, and ALD AlN are used most often, and offer the greatest promise for the AlGaN/GaN heterostructures. The influence of the passivation of the ALD Al2O3, SiNx, and SiON coatings of various thicknesses on the change of the charge and the density of the states of the AlGaN/GaN heterostructures is investigated. The physical parameters of the structures are estimated by the C–V characteristics measured on various frequencies and the I–V characteristics. It is demonstrated, according to the examined energy band diagrams of the structures at various control voltages, and estimation of the elemental composition of the films by the method of Auger electron spectroscopy, that the reason for the generation of a high positive charge at the deposition of the ALD Al2O3 and SiNx films is the occurrence of an additional piezoelectric charge in the buffer layer of AlGaN. It is demonstrated that use of the SiON films with the oxygen concentration in them higher than 3% does not result in the generation of an additional positive charge but can initiate current fluctuations during the measurement of the I–V characteristics. A possible mechanism of carrier transport in the space charge region resulting in such fluctuations is discussed.

The effect of a mixture’s composition on the electrophysical parameters and emission spectra of HCl/Cl2 and HCl/He plasmas under the conditions of a DC glow discharge is analyzed. The data on the gas temperature and reduced electric field strength are obtained. It is established that the reduced electric field strength in HCl/Cl2 plasma rises linearly with the rising fraction of the second gas in the mixture, while the same value in the HCl/He plasma decreases. It is shown that, in the HCl/Cl2 plasma with a variable composition, the atomic chlorine concentration remains practically unchanged, whereas, in the HCl/He plasma, it decreases monotonically.

A short survey on experimental works in quantum cryptography is presented. We describe experimental setups that were designed in the Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, for quantum key distribution through an air space and along a fiber-optic communication line. The results of the study of quantum efficiency parameters, probability of afterpulse appearance, and noise levels for different operation modes of InGaAs-InP avalanche photodiodes are presented.

The kinetics and mechanisms of reactive ion etching of titanium oxides (TiO2), indium (In2O3), tin (SnO2), and zinc (ZnO) in HBr + Ar plasma. It is found that an increase in the fraction of Ar is accompanied by a decrease in the etching rates of all the materials under study, while the absolute values of the rates for any composition of the mixture are correlated to the value of the breaking energy of the oxide bond and/or the volatility of the interaction products. With the combined use of methods of diagnostics and plasma modeling, the stationary concentrations of active particles and the density of their fluxes on the treated surface are determined. The use of these data for the analysis of the kinetics of heterogeneous processes showed that (a) the dominant etching mechanism in the range 0–75% Ar is an ion-stimulated chemical reaction; and (b) the effective probability of the interaction of bromine atoms increases (for TiO2) or decreases (for In2O3, SnO2, and ZnO) with the increasing dilution of HBr with argon. Assumptions are made about the reasons for this dependence.

Modern models that are used to describe the processes of elastic, quasi-elastic, and inelastic scattering are considered. For elastic scattering, various forms of the electrostatic interaction potential, the exchange interaction potential, and the correlation-polarization potential are presented. For quasi-elastic processes, including electron-phonon and electron-polaron scattering, a model based on the theory of dielectrics and an empirical model are presented. Inelastic scattering is described based on the energy loss function, which is constructed using three different approaches.

The theoretical and experimental analysis of phase equilibria in the Zn–Se–Fe ternary system is carried out with the use of X-ray diffraction analysis and inductively coupled plasma mass-spectrometry. Information is acquired on monovariant equilibria in isothermal sections at temperatures of 730, 814, and 1073 K and also on the solubility of iron under conditions of bi- and monovariant equilibria at 1073 K. The phase composition of samples in the Zn–Se–Fe system synthesized at different temperatures and different total compositions is determined. The reliability of theoretically plotted isothermal sections in the Т–Х–Y projection of the P–T–Х–Y diagram for the Zn–Se–Fe ternary system is confirmed.

The technology to obtain a silicide Pt/Ir mixture and Pt/Ir–Si photosensitive structures with a Schottky barrier in the middle IR area is developed. It is found that the main way to detect Pt/IrSi–р–Si structures is through the photoemission of Pt/IrSi holes into silicon. Moreover, the maximal photosensitivity is observed when the Pt/IrSi is not thicker than the free path length of the holes (less than 460 Å). The energy band diagram of the Schottky barrier structures based on the Pt/IrSi–Si contact is plotted. It is determined that the electron affinity of Pt/IrSi varies within 4.7–5.26 eV depending on the operational conditions of its formation.

Các transistor graphene hiệu ứng trường (FGTs) dựa trên graphene đơn lớp được mô phỏng bằng mô hình tự nhất quán kết hợp đơn giản đã được phát triển. Mô hình này được sử dụng để so sánh kết quả tính toán đặc tính dòng-điện (I-V) của năm thiết bị có cùng tham số hình học nhưng lại sử dụng các vật liệu khác nhau cho dielectrics cổng phía trên. Ảnh hưởng của độ dày của dielectrics của cổng phía trên và phía dưới đến đặc tính I-V truyền của FGTs hai cổng đã được phân tích.