This article presents the results of modeling the heterostructure of a normally-off n-channel transistor with various designs of field plates on electrodes. The use of field plates makes to possible to effectively control the distribution of the field in the channel and increases the breakdown voltage. The optimal design parameters of field plates to achieve maximum BV were determined by study of the current-voltage characteristics, the distribution of the field in the channel and the concentration of the majority carriers in the channel.

Structures based on suspended graphene are promising elements for problems in photonics and sensory electronics due to the possibility of the elimination of trap states in the substrate and the increase in the speed and sensitivity of the graphene layer. The development of techniques for introducing carbon nanostructures in silicon technology to create micro- and nanoelectronic devices is also relevant. In this paper, the features of the technique for the formation of a silicon membrane and pores in it, as well as the deposition of graphene on silicon membranes, are presented. The Raman spectra of suspended graphene showing a shift of the G-peak by 4.5 cm–1 and the 2D peak by 7.5 cm–1 relative to the peaks of the graphene lying on silicon are obtained. Using the curves of the approach and retraction of the probe of an atomic force microscope, the possible deflection of the suspended graphene is studied, showing the distances at which the attractive and repulsive forces are located in the probe–suspended graphene system. It is established that the significant deflection of graphene, by 1 µm at a pore diameter of 5 µm, makes laser focusing is difficult. This primarily affects the use of such structures as a base for a gas or fluid sensor of various organic compounds, as well as for suspended graphene-based transistors.

The work is devoted to the study of high electron mobility transistor (HEMT) based on gallium nitride (GaN) in order to find the optimal composition and thickness of the buffer layer for the development of a power normally-off transistor with the highest possible breakdown voltage. The study was carried out using Sentaurus Device software (TCAD). The work shows the dependence of breakdown voltage on modifications made to the design. In particular, it has been established that to achieve breakdown voltages of the order of 1000 V, it is necessary to have an AlGaN buffer layer in GaN HEMT with a thickness of at least 4 µm, an aluminum mole fraction of about 5

This article presents the results of simulation the heterostructure of normally-off p-channel transistor. The design of the upper layers of the heterostructure was determined to induce the appearance of a 2DHG at the p-GaN/AlGaN heterojunction. By studying the band diagrams, the dependence of the transistor behavior on the thickness of the p-GaN and the impurity concentration within it is demonstrated for the p-channel device. Additionally, through analysis of the current-voltage characteristics the relationship between the formation of a normally-on or normally-off transistor and the thickness of the p-GaN layer, as well as the impurity concentration within it, was determined.

В статье рассмотрены ключевые зависимости характеристик нормально-закрытых тран- зисторов от параметров GaN гетероструктур. Определены толщины и концентрации легирующих примесей в слоях гетероструктуры. В результате моделирования получены вольтамперные характеристики р-канального полевого транзистора и n-канального транзистора с подзатворным слоем р-типа.

The lithographic methods are used to form contacts for nanostructures smaller than 100 nm , in part, e-beam lithography and focused ion beam lithography with the use of electron-sensitive resist. Focused ion beam lithography is characterized by greater susceptibility to resist, high value of backward scattering, proximity effect, and best ratio of speed performance and contrast to exposed elements’ minimal size, compared to e-beam lithography. In this work, a method of ultrathin resist exposure by focused ion beam is developed. Electron-sensitive resist thickness dependence on increase of its toluene dilution was established. It was shown that electron-sensitive resist thinning down to 30 μm based on α-chloro-methacrylate with α-methylstyrene allows the 500-nm gapped metal contacts formation over a span of 30 μm. Silicon nanostructures within metallic nanoscale gap on dielectric substrate have been obtained. The geometry of obtained nanostructures was studied by optical, electron, ion, and probe microscopy. It has been established that it is possible to not use additional alignment keys when nanoscale field-effect transistors are created based on silicon nanostructures.

В работе рассмотрены технологические особенности изготовления омических контак- тов с сопротивлениями от 0,025 до 0,4 Ом ∙ мм к наногетероструктурам на основе нитрида галлия. Установлено, что невжигаемые омические контакты являются наиболее подходящими для освоения рабочих частот вплоть до терагерцового диапазона.

A carbon nanotubes (CNT) network is a promising gas sensing material for "e-nose" development due to the vast methods of cross-sensitivity modification. However, the dominant sensitivity mechanism remains unclear since both the CNTs and junctions between CNTs can be gas-sensitive. In this paper to estimate the contributions of both mechanisms, we simulated CNT networks with varied densities using an equivalent electrical circuit. Density variation alters the junction's and CNT's contribution to the network resistance, and hence the total resistive response. We compared the results with the experimental resistive response of the spray-coated CNT networks toward ammonia (NH3). A decrease in the network density results in a higher response, which indicates a likely significant role of CNTs junctions in sensitivity of a sparse networks. We also studied the effect of formic acid treatment on CNT networks, which increases both conductivity and sensitivity by removing residual solvent.

In this work, we consider the formation of a sensor layer 100 nm thick based on platinum-doped tin oxide. We investigated the method of forming an oxide film using magnetron sputtering Sn and Pt in Ar+O2 plasma. Using X-ray diffraction, it was found that the film consists of nanoscale particles with a metal core. The average size of the nanoparticles forming the film was from 47 to 74 nm The characteristics of the film were measured during additional oxidation in the temperature range from 300 to 700 °C. Thanks to annealing, the resistance of the sensor layer can be varied from 10 kΩ to 100 MΩ at a detection temperature of 300 °C The optimized film has been tested to detect ethanol, acetone, and ammonia at streams of 50, 100, 150 ppm.

Представлены результаты изучения морфологии поверхности и структуры слоев AlN, сформированных аммиачной МЛЭ на темплейтах 3C-SiC/Si(111) on-axis- и 4° off-axis-разориентации. Опробован технологический режим низкотемпературной эпитаксии зародышевого слоя AlN на поверхности 3C-SiC(111). Среднеквадратичная шероховатость поверхности (5 х 5 мкм) слоев AlN толщиной 150 ± 50 нм составила 2,5-3,5 нм на темплейтах 3C-SiC/Si(111) on-axis и 3,3-3,5 нм на 4° off-axis. Показано уменьшение шероховатости смачивающего слоя AlN при изменении скорости роста. Получены монокристаллические слои AlN(0002) со значениями FWHM (ω-геометрия) 1,4-1,6°. The paper presents the surface morphology and crystal structure of AlN layers formed by ammonia MBE on 3C-SiC/Si(111) on-axis and 4° off-axis disorientation. It offers the technological approach of low-temperature epitaxy of the AlN nucleation layer on the 3C-SiC (111) surface. Root mean square roughness (5 х 5 |xm) of AlN layers with thickness of 150 ± 50 nm was 2,5-3,5 nm onto on-axis templates and 3.3-3.5 nm onto 4° off-axis. It appears that the RMS roughness of the AlN surface is changing with the growth rate variation. Single-crystal AlN(0002) layers with FWHM values (ω-geometry) of 1.4-1.6° have been obtained.

Abstract—In this article, we studied the growth characteristics of AlN epitaxial layers on 3С-SiC/Si(111) templates at various values of atomic flux of aluminum at a constant growth temperature and a constant flow of atomic nitrogen. The AFM method was used to study the morphology of the resulting structures. The minimum roughness was achieved at a growth rate of 150 nm/h on on-axis templates, and at 90 nm/h on off-axis templates. Epitaxial layers of hexagonal AlN with root mean square roughness of less than 3 nm were obtained on 3С-SiC/Si(111) templates with a diameter of  100 mm, in which there was no grain structure. Single-crystal AlN (0002) layers with FWHM (ω‑geometry) values of about 1.4° were obtained.

Technique based on FIB and PCE for the formation of nanoscale silicon fins on silicon-on-sapphire structures was demonstrated. The stability of the obtained mask to PCE was investigated depending on the dose of ionic exposure. It was found that the Si fin 150 nm in height and a width of less than 40 nm was obtained by implantation of Ga+ ions with a dose of 3 square 1017 to 4 square 1017 CM-2. Current-voltage characteristic of contacts to nanosized fins was researched. The gate dielectric Al2O3 2-3 nm thick was deposited by the ALD method. In the created prototypes of the transistor, the length of each channel was 1.2 mu m, and the gate - 100 nm. The obtained I-V characteristics prove the good controllability of the channel in the nanosized fin and demonstrate the operability of the devices.

Results of surface morphology and crystalline structure had shown for Ga(Al)N layers which was grown by MBE on 3C-SiC/Si(111) virtual substrates with on-axis and 4 degrees off-axis orientation. Roughness values had increased up to similar to 7 nm for on-axis and to similar to 5 nm for 4 degrees off-axis orientation after 560 nm deposition of GaN. Monocrystalline GaN(0002) was verified by co-rocking curve measurement with FWHM 0.61-0.76 degrees for on-axis and 0.55-0.65 degrees for 4 degrees off-axis orientation. Wafer bow shown the ascending up to similar to 18 mu m for on-axis and similar to 12 mu m for 4 degrees off-axis orientation and tensile strain for all samples had been confirmed.

Stimulated low frequency Raman scattering (SLFRS) in submicron single-crystal diamond films (SCD) with a graphitized layer built-in is investigated. The value of SLFRS frequency shift lies in gigahertz range (8.4-9.3 GHz) and shows the morphological dependence (inverse dependence on the thicknesses of SCD layers). Experimentally estimated SLFRS conversion efficiency and threshold evidence about the coherent phonon mode excitation in submicron SCDs as a result of nonlinear interaction of high-power laser wave with an eigen vibration of nanosized graphitized layer built-in.

Spectral characteristics of spontaneous Raman scattering in the submicrometer diamond membrane grown by the hydrogen implantation method are studied in comparison with the single-crystal diamond matrix. A shift in the main line of diamond one-photon excitation (sp 3-hybridization) at a frequency of 1324 cm−1 is revealed in the diamond membrane. This fact indicates multiple internal strains (residual compression strains) due to residual defects and is a concequence of the use of the hydrogen implantation method (hydrogen is implanted into diamond to form a sacrificial layer.

Stimulated low frequency Raman scattering (SLFRS) in single-crystal diamond films (SCD) with a graphitized layer built-in is investigated. SLFRS process in all studied structures has frequency shift in gigahertz range (5.1-13.2 GHz). Coherent phonon mode excitation at a frequency of several GHz is a result of nonlinear interaction of high-power laser wave with submicron films. SLFRS conversion efficiency and threshold is estimated experimentally. Comparison of the obtained results with data on SLFRS properties in synthetic opal matrixes is made.

We report the first experimental observation of high-efficient phonon-mode coherent excitation using stimulated low-frequency Raman scattering (SLFRS) in submicron diamond{graphite{diamond heterostructure films with an ion-beam-induced graphitized layer. We show that the SLFRS process in submicron diamond heterostructures has a frequency shift in the gigahertz range and estimate experimentally the SLFRS conversion efficiency and threshold.

This study is devoted to the fabrication of molecular semiconductor channels based on polymer molecules with nanoscale electrodes made of single-walled carbon nanotubes. A reproducible technology for forming nanoscale gaps in carbon nanotubes using a focused Ga + ion beam is proposed. Polyaniline molecules are deposited into nanogaps up to 30 nm wide between nanotubes by electrophoresis from N-methyl-2-pyrrolidone solution. As a result, molecular organic transistors are fabricated, in which the field effect is studied and the molecular-channel mobility is determined as 0.1 cm 2 /(V s) at an on/off current ratio of 5 × 10 2 .

Работа посвящена созданию молекулярных полупроводниковых каналов на основе полимерных молекул со сформированными наноразмерными электродами из однослойных углеродных нанотрубок. Предложена воспроизводимая технология формирования наноразмерных зазоров в углеродных нанотрубках с помощью фокусированного ионного пучка Ga+. В сформированные между нанотрубками нанозазоры с шириной до 30 нм под действием электрофореза осаждались молекулы полианилина из раствора в 1-метил-2-пирролидоне. В результате были созданы молекулярные органические транзисторы, в которых исследован полевой эффект и определена подвижность молекулярного канала, равная 0.1 см2/В·с при отношении токов включения и выключения 5·102. DOI: 10.21883/FTP.2017.04.44344.8383