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A hypothesis on the possible occurrence of the superplasticity phenomenon in local zones of friction contact is put forwarded. An extended classification of friction junctions is developed with consideration for the superplasticity phenomenon. A relation for the coefficient of friction which considers the possibility of the occurrence of the superplasticity phenomenon over a portion of the friction surface is obtained.

One- and two-step syntheses of composite coatings with an A–OOO polyimide matrix filled with 40-nm tungsten disulfide nanoparticles produced using gas-phase synthesis, which are intended for operation under dry friction conditions, are described. Results of studying the tribological behavior of these coatings are presented.

For the English abstract and full text of the article please see the attached PDF-File (English version follows Russian version).ABSTRACT The duration of sorting of the train on the turnout track is determined by the known formula Tsort = A•g + B•m. At the same time, the duration of all semi-trips - arrival of the locomotive behind the part of the train, its extension to the turnout track, sorting and reverse pulling of the remaining cars - were calculated according to the formula ts/t = a + bm, which is now replaced by a new method for adjusting the shunting operations. The article presents the results of a study that made it possible to derive a formula for calculating the duration of the sorting of a train on the turnout track based on a different calculation of the duration of semi-trips. Keywords: railway, turnout track, duration of sorting, duration of semi-trip, calculation formulas. REFERENCES 1.Time norms for shunting operations performed at railway stations of JSC Russian Railways, standards for the number of shunting locomotive crews (2007) [Normy vremeni na manevrovye raboty, vypolnjaemye na zheleznodorozhnyh stancijah OAO «RZhD», normativy chislennosti brigad manevrovyh lokomotivov (2007 g.)]. 2.Order of the Ministry of Railways of the Russian Federation dated September 29, 2003, No.67 «On approval of the procedure for developing and determining the technological terms of turnover of cars and technological norms for loading cargo into cars and unloading cargo from cars» [Prikaz MPS RF ot 29 sentjabrja 2003 g. № 67 «Ob utverzhdenii porjadka razrabotki i opredelenija tehnologicheskih srokov oborota vagonov i tehnologicheskih norm pogruzki gruzov v vagony i vygruzki gruzov iz vagonov»]. 3.Kochnev, F.P., Sotnikov, I. B. Management of the operational work of railways: educational guide for universities [Upravlenie ekspluatacionnoj rabotoj zheleznyh dorog: Ucheb. posobie dlja vuzov].Moscow, Transport publ., 1990, 424 p. 4.Shmulevich, M.I., Starikov, A. E. Features of Regulation of Shunting Operations in the Station Simulation Model.World of Transport and Transportation, Vol.13, Iss.5, pp.198-212. 5.Shmulevich, M.I., Starikov, A. E. Structure of the simulation model of an industrial railway station and its implementation in the AnyLogic system [Struktura imitacionnoj modeli promyshlennoj zheleznodorozhnoj stancii i ee realizacija v sisteme AnyLogic].Promyshlennyj transport XXI vek, 2016, Iss.3-4, pp.20-24. 6.The AnyLogic Company.2015.AnyLogic - Multimethod Simulation Software.[Electronic resource]: http://www.anylogic.com.Last accessed 29.10.2015. 7.Petersen, E.R.Railyard Modeling: Part I.Prediction of Put-Through Time, Transportation Science, 1977, vol.11, no.1, February. 8.Baugher, R.Application of Any Logic to Railroad Operation Analysis.Any Logic Conference, December, 2013. 9.Lin, E., Cheng, C.Yard Sim.A Rail Yard Simulation Framework and its Implementation in a Major Railroad in the U.S.Proceedings of the 2009 Winter Simulation Conference // Edited by M.D.Rossetti, R.R.Hill, B.Johansson, A.Dunkin, R.G.Ingalls.Piscataway, New Jersey, Institute of Electrical and Electronics Engineers, Inc.2009, pp.2532-2541. 10.Clausen, U., Goedicke, I.Simulation of Yard Operations and Management in Transshipment Terminals.Proceedings of the 2012 Winter Simulation Conference.2012. 11.Kiseleva, M. V. Simulation modeling of systems in Anylogic environment.Teaching-methodical manual [Imitacionnoe modelirovanie sistem v srede Anylogic. Uchebno-metodicheskoe posobie].Ykaterinburg, USTU-UPI, 2009, 88 p.

A synthesis is described and tribological characteristics are presented for composite coatings 40 μm thick with a PM–DADPE polyimide matrix and a filler of tungsten disulfide nanoparticles with size of 4 nm and tungsten diselenide nanoparticles 60 × 5 nm in size obtained via gas-phase synthesis.

We investigate the shortening of the gate-length in submicrometric and nanometric field-effect transistors as a powerful tool to improve their self-oscillations performances in the terahertz frequency region due to the appearance of the Dyakonov–Shur instability. The theoretical model is based on the numerical solution of hydrodynamic equations for the electron transport in FETs/HEMTs channels. We show that a decrease of the gate length allows, on the one hand, to increase the intrinsic resonant frequencies near 1 THz and, on the other hand, to improve the conditions for the onset of the Dyakonov–Shur instability and related phenomena. The small-signal characteristics calculated under constant drain-voltage operation are compared with the drain-voltage self-oscillations calculated under constant drain-current operation.

Electron transport and drain current noise in optimized for THz generation wurtzite GaN MOSFET have been studied by Monte Carlo particle simulation which simultaneously solve the Boltzmann transport and pseudo-2D Poisson equations. The drain current and average electron energy under the gate at 300 K is calculated as a function of drain bias. The electron cooling when average electron energy under the gate is less than thermal electron energy is demonstrated. The step like current voltage relation due to the optical phonon emission is shown. It is found that THz generation in frequency range from 6 to 10 THz is possible at room temperature.

Electron transport and drain current noise in the wurtzite GaN MOSFET have been studied by Monte Carlo particle simulation which simultaneously solves the Boltzmann transport and pseudo-2D Poisson equations. A proper design of GaN MOSFET n+nn+ channel with uncentered gate in n-region to reach the maximum detection sensitivity is proposed. It is shown that the main role in formation of longitudinal transport asymmetry and THz radiation detection is played by optical phonon emission process. It is found that the detection current at 300 K is maximal in frequency range from 0.5 to 7 THz. At higher frequenciea the detection current rapidly decreases due to the inertia of electron motion.

We present a theoretical investigation of high-frequency electronic noise in field-effect transistors used as detectors of TeraHertz radiation. Calculations are performed using the hydrodynamic-Langevin approach and specialized to the case of InGaAs high-electron mobility transistors. The main physical phenomena associated with the effect of branching of the total current between channel and gate and the appearance of two-dimensional plasma waves are discussed. We demonstrate that thermally excited standing plasma waves originate series of resonant peaks in the corresponding noise spectral densities whose presence can be controlled by the embedding circuit. A significant damping of the high-frequency excess noise is found when the transistor is submitted to a two-lasers optical photo-excitation presenting a beating frequency in the TeraHertz range. Finally, we discuss the dependence of the damping effect, as well as a shift of the resonance peaks from the presence of channel ungated regions.

We analyze electronic noise in field-effect transistors associated with plasma waves in the terahertz frequency domain by using a numerical approach based on the coupled hydrodynamic and Poisson equations. The current and voltage noise spectra, calculated by means of the transfer impedance method, exhibit a series of peaks associated with two- and three-dimensional plasma resonances. The two-dimensional plasma peaks have been found to depend on the channel length including gated and ungated regions. Under asymmetric boundary conditions, electrical instabilities characterized by terahertz oscillations of the drain voltage and gate current can be reached at sufficiently high values of the total drain current. A resonant enhancement of the plasma peaks in the noise spectra has been found to be a precursor of the instability onset. Through a spatial analysis of the local contributions we have shown that the main contribution to the total noise at frequencies near the plasma resonance comes from the ungated n-region placed between the source and the gate contacts.

We survey recent results on electronic noise in nanostructured devices. Three kinds of excess noise referring to hot-carriers in submicron n+nn+ diodes, shot noise in mesoscopic structures, resistance fluctuations in thin film conductors, are considered. The influence of down-sizing on fluctuations is illustrated in each case.

The problems related with the intrinsic noise in FET/HEMT channels induced by continuous branching of the total current between channel and gate are considered in the framework of a simple analytical model and its predictions on the current-noise spectra. Main branching-induced effects such as the appearance of an additional noise related to the excitation of plasma waves, its dependence on FET/HEMT embedding circuits, interference properties, etc. are analysed.

Possibilities and advantages of the electro-optical sampling (EDS) technique for the investigation of excitation of THz-range 2D plasma waves in FET/HEMT channels are considered both experimentally and theoretically. It is experimentally demonstrated that the EOS technique allows one to identify an excitation of 2D plasma waves in the HEMT channel under a given working point determined by external embedding circuits. Theoretical simulations show that the development of the instability of 2D plasma waves can be easily identified in the framework of the EOS technique.

The plasma instabilities (PI) are promising mechanisms for high frequency microwave generation in semiconductor nnn structures. The two types of PI at near collisionless (NCL) and optical phonon emission dominated (OPED) electron transport conditions in the nnn structures are considered by Ryzhij et al. [1]. They found that both types of PI’s can lead to current self-oscillations up to the plasma frequency, which depends on the carrier concentration in the n-region of the nnn structure (see Ref. [1] and references therein). The regularity of selfoscillations is sensitive to the spatial resonance conditions for space charge waves periodically growing and decaying due to the PI, i.e. there exists the optimum length of n-region at the given doping of this region. In real nnn structures the OPED and especially NCL plasma instabilities are suppressed by the lattice (mainly due to accoustic phonons) and impurity scatterings. However, the progress in manufacturing structures with remote doped conducting channels recently gave the second breath to PI investigations. Also the recent achievements in THz frequency noise measurements have opened new directions in PI investigation. It is well known that the noise spectrum contains integrated information about physical processes such as carrier scattering, various instabilities, including PI, etc. Therefore, the identification of noise spectrum pecularities such as the peaks in the noise spectra related to the certain process is important.

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Electron transport and drain current noise in wurtzite GaN MOSFETs have been studied by Monte Carlo particle simulations which simultaneously solve the Boltzmann transport and pseudo-2D Poisson equations. It is shown that at positive gate voltages giving excess electron concentration in the n-region of the channel the drain current, self-oscillations in the THz frequency range up to 5 THz are possible. These self-oscillations are driven by electron plasma instability. Moreover, a step-like drain current dependence on drain bias is demonstrated.

We investigate by means of Monte Carlo simulations the physical processes associated with the emission of TeraHertz radiation in different electronic devices. We analyze four alternative and complementary strategies which seem to be promising candidates to obtain the TeraHertz emission: (1) a nitride maser based on the optical-phonon transit-time resonance, (2) the high–order harmonic generation in bulk materials and nanometric Schottky-barrier diodes, (3) the excitation of coherent plasma oscillations in micron and submicron diodes, (4) the current instabilities and plasma oscillations in high electron mobility transistors (HEMT). The numerical results show that several physical mechanisms can be exploited to increase significantly the operating frequency of these devices and the best conditions to optimize the radiation emission in the TeraHertz range are studied in detail.

Electron transport in long (up to 15 μm) InN nnn structures is theoretically investigated by the Monte Carlo particle technique at low lattice temperatures when optical phonon emission is the dominating scattering mechanism. It is shown that at constant bias a free-carrier grating can be formed inside the n-region. Such a grating is found to be responsible for microwave power generation in the THz frequency range. The generation mechanism is similar to that in submicron nnn structures under quasiballistic transport conditions.

International audience; The low-field mobility spectrum and related quantities is calculated for a nonparabolic band by using the exact solution of the linearized Boltzmann transport equation within the relaxation time approach. Numerical calculations are applied to bulk nitrides at different lattice temperatures and impurity concentrations.

To qualify the feasibility of standard semiconductor materials and Schottky‐barrier diodes (SBDs) for THz high‐order harmonic generation and extraction, the harmonic intensity, intrinsic noise and signal‐to‐noise ratio are calculated by the Monte Carlo method when a periodic high‐frequency large‐amplitude external signal is applied to a semiconductor device. Due to very high signal‐to‐noise ratio heavily doped GaAs SBDs are found to exhibit conditions for frequency mixing and harmonic extraction that are definitively superior to those of bulk materials. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The conditions for THz radiation generation caused by electron transit-time resonance in momentum and real spaces under optical phonon emission are analyzed for nitride-based materials and their structures. It is shown that such a mechanism provides a unique possibility to realize sub-THz and THz radiation generation at the border between the electro-optical and electronic techniques by using two alternative approaches: (i) amplification of transverse electromagnetic waves in 3D bulk materials and 2D quantum wells, and (ii) longitudinal current-field instabilities in sub-micron and micron n(+)nn(+) diodes. Estimations of frequency regions, output power and efficiency of the generation demonstrate that nitrides are promising materials for THz radiation generation.

We present an analytical model suitable for the study of the plasma modes in gated semiconductor slabs of arbitrary thickness. A pseudo-two-dimensional Poisson equation allows us to consider both transverse and longitudinal electric field variations. We calculate the dispersion relation demonstrating the dispersive nature of the slab. We express the frequencies of the plasma modes appearing in a cavity. A transition from a two-dimensional to a three-dimensional behavior is revealed when the transverse dimension of the device or the order of modes grow. These analytical results show a good agreement with Monte Carlo calculations of the voltage noise spectrum.

Electron transport in InN n+nn+ diodes is investigated by the Monte Carlo Particle technique at temperatures below about 80 K, when optical phonon emission is the dominating scattering mechanism. It is shown that at constant bias, high enough to force strong electron optical phonon interaction but below the threshold value for intervalley transfer processes, the profiles of the relevant physical quantities exhibit a periodic spatial behaviour in the n-region, thus leading to the formation of a superlattice like structure. Such a structure is found to be responsible for microwave power generation in the THz frequency range.

To qualify the feasibility of standard semiconductor materials and Schottky-barrier diodes (SBDs) for THz high-order harmonics generation and extraction, the noise-to-signal ratio is calculated by the Monte Carlo method. Heavily doped GaAs SBDs are found to exhibit conditions for frequency mixing and harmonics extraction which are definitively superior to those of bulk materials.

International audience; The feasibility of bulk semiconductors subjected to strong periodic electric fields for terahertz radiation generation due to the high-order harmonic extraction is analyzed by using Monte Carlo simulations. The high-order harmonic intensity and the spectral density of velocity fluctuations are calculated for GaAs, InP, and InN. By comparing the harmonic intensity with the noise level the threshold bandwidth for high-order harmonic extraction determined by their ratio is introduced and evaluated for the above materials. The results show that semiconductor materials with a high value of the threshold field for the Gunn-effect are characterized by a high value of the threshold bandwidth under high-order harmonic generation and, hence, they are promising materials for microwave generation in the THz frequency range by high-order harmonic extraction.

The kinetic corrosion characteristics of 35ХН2МФА-Ш, 30ХН2МФА, and 30ХРА steels with rust-preventive compounds applied are investigated in an industrial neutral electrolyte, depending on whether a compound is infected with microorganisms or not. The effect of microorganisms and their metabolites on the corrosion of steels greased with the compounds are assessed.

Streaming plasma instability at near ballistic electron motion in InN n + -n - -n-n + structures is theoretically investigated by the Monte Carlo particle technique at low lattice temperatures (T < 140 K), when dominating scattering mechanism is the optical phonon emission. It is shown that the electron transport through the structure of certain geometry can be essentially nonstationary in some bias range. The simulation of the steady state transport and microwave power generation in InN n + -n - -n-n + structures, connected with an external parallel resonant circuit, demonstrates that up to 50 μW of the microwave power can be delivered by the structure in the 1.1 to 1.2 THz frequency range at liquid nitrogen temperature.

The high-order harmonics generation in bulk InN, subjected to a high-frequency alternating electric field of strong-amplitude is investigated theoretically using Monte Carlo simulations of carrier interacting with a multi-mode electric field. This approach allows on the one hand to account in a natural way for the effect of the reabsorption of the generated radiation by the nonlinear medium itself, and on the other hand to estimate the constraints, which must be satisfied by the external experimental setup to achieve the maximum conversion efficiency. It is demonstrated, that InN is a promising material for such a conversion up to the THz frequency range. Under optimum conditions, the power conversion efficiency is found to reach several percents.

In this paper, the conditions for microwave power generation caused by the quasi-periodic motion of carriers under the combined action of carrier acceleration in a constant electric field and optical phonon emission at low temperatures are analysed by Monte Carlo simulations of both small- and large-signal responses in bulk nitrides such as InN, GaN and AlN. The results show that due to strong carrier-phonon interaction bulk nitrides are promising materials for THz radiation generation.

The 4H-SiC transferred electron device with the p-layer at the cathode is proposed and simulated by Monte Carlo particle technique. The very high 400 GHz power can be delivered by the device. The simulation show strong dependence of the generation on the contact resistance R c . The generation threshold current and bias increase exponentially with R c increased, what leads to the increased energy dissipation in the device. For low energy dissipation the value R c < 10 -6 Ωcm 2 is needed.

Streaming plasma instability at near ballistic electron motion in InN n + n - nn + structures is theoretically investigated. At low lattice temperatures (T < 140 K), when dominating scattering mechanism in InN is the opticall phonon emission the electron transport through the structure of certain geometry can be essentially nonstationary in some bias range. By Monte Carlo particle technique the steady state transport and microwave power generation in InN n + n - nn + structures connected with external parallel resonant circuit are simulated. It is demonstrated that over hundred microwatt of the microwave power can be delivered by the structure in 1.1 ∼ 1.2 THz frequency range at liquid nitrogen temperature.

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Electron transport and drain current noise in field effect transistor with nnn InP channel have been studied by Monte Carlo particle simulation which simultaneously solves the Boltzmann transport and pseudo-2D Poisson equations. It is shown that at gate voltages giving excess electron concentration in n-region of channel the drain current self-oscillations in THz frequency range are possible. The self-oscillations are driven by electron plasma instability.

In modern FET/HEMT structures the Gunn-effect is not usually considered as one of the mechanisms able to realize high-frequency (near terahertz (THz)) oscillations of the current. Physically, the effect is caused by the suppression effect of the remote Coulomb interaction which takes place in the gated region of the conducting channel. In the present work we propose a way to overcome this limitation by using the impact ionization effect. It is shown by Monte Carlo simulation that the impact ionization in MOSFET structures allows us to get near THz oscillations.

Electron transport and microwave power generation in the 200-300 GHz frequency range by n+-n--n-n+ zincblende GaN and n+-p-n-n--n+ wurtzite GaN structures have been studied by a Monte Carlo particle simulation which solves the Boltzmann transport and Poisson's equations along with equations governing the associated circuit elements and parasitic contact resistance. It is shown that at 300 K in the 230-250 GHz frequency range over 350 mW microwave power can be delivered by the n+-p-n-n--n+ wurtzite GaN structure in continuous wave operation mode and over 1.3 W in pulsed mode.

The conditions for microwave power generation under the quasi-periodic motion of carriers caused by the combined action of carrier acceleration in a constant electric field and optical phonon emission at low temperatures are analysed by means of Monte Carlo simulations of both small- and large-signal responses in bulk nitrides such as GaN and InN. It is shown that, as a consequence of the high value of the optical phonon energy and the strong electron-phonon interaction, a dynamic negative differential mobility caused by transit-time resonance occurs over a wide frequency range which covers practically the whole submillimetre range and persists in the THz frequency range up to liquid nitrogen temperature. The efficiency of the amplification and generation is found to depend nonmonotonically on: (i) the static and microwave electric field amplitudes, (ii) the generation frequency, and (iii) the carrier concentration. Accordingly, for each generation frequency there exists an optimal range of parameter values. Under optimal conditions we predict a generation efficiency of about 1-2% in the 0.5-1.5 THz frequency range.

The conditions for microwave power generation at low temperatures under optical phonon emission are analyzed by Monte Carlo simulations of both small- and large-signal responses in bulk zinc blende and wurtzite GaN. As a result of the high optical phonon energy and the strong interaction of electrons with optical phonons in GaN a general improvement on the transit-time resonance and a considerable increase in the maximum generation frequency and power can be achieved in comparison to the widely studied III–V materials such as GaAs and InP. A dynamic negative differential mobility caused by transit-time resonance occurs in a wide frequency range of about 0.05–3 THz and persists in the THz frequency range up to the liquid nitrogen temperature with doping levels up to about 5×1016 cm−3. The efficiency of the amplification and generation is found to depend nonmonotonously on static and microwave electric field amplitudes, generation frequency, and doping level so that for each generation frequency there exist...

The classical impedance field method is one of the most powerful techniques to calculate electronic noise in semiconductor structures. This method fails when applied to deep submicron devices due to the presence of spatial correlations between noise sources. To overcome this drawback, a new technique (generalised impedance field) has been developed in the frame of a hydrodynamic simulator. Analogously to the classical method, the calculation of electronic noise requires the knowledge of two quantities: the local noise sources and the generalised impedance fields. Instead of using a hydrodynamic approach to obtain the generalised impedance fields and a Monte Carlo simulation for the noise sources, we have used a microscopic simulator (the Scattered Packet Method) to compute both quantities.

The aim of this work is to calculate the amplification band and the maximum gain for an optical phonon transit-time resonance (OPTTR) maser based on bulk zincblende and wurtzite GaN. For this sake the response function of the longitudinal velocity in the time domain representation is obtained by an extended averaging over the before- and after-scattering ensembles during Monte Carlo simulations. Then the differential mobility spectrum is calculated by Fourier transformation. In the frequency region of dynamic negative differential mobility (DNDM), the gain is determined and we investigate its dependence on frequency, applied electric field, lattice temperature, and doping level.

A Monte Carlo particle (MCP) bipolar model for 4H-SiC consisting of three electron and two hole bands is developed to simulate the millimetre wave power generation by 4H-SiC IMPATT diodes. Validation of the model is provided by comparing (i) carrier transport properties with full band simulation results and (ii) hole impact ionization coefficients with the most recent experimental results. MCP simulation results are reported for a low-voltage 4H-SiC IMPATT diode connected directly in a parallel resonant circuit with a standard 50 O load resistor. The detailed evolution of carrier generation, accumulation and drift are presented to confirm the design of an efficient hi-lo IMPATT diode structure. Critical performance parameters investigated include bias and frequency dependences of millimetre wave output power, generation efficiency, conduction current and frequency stability at an operating frequency around 200 GHz. It is predicted that very high-power millimetre waves at around 200 GHz can be generated at pulse mode.

A universal description of the OPTTR-assisted generation band of THz radiation is developed in the framework of a 3D transport in bulk materials and 2D transport in QWs and HLs. On the one hand, in the framework of an ideal streaming motion we have carried out an analytical investigation based on phonon scattering rates: namely, elastic deformation acoustic phonons in the passive energy region below the optical-phonon energy 0 and emission of polar optical phonons in the active energy region, 0. On the another hand, quantitative estimations of the qualitative constraints given by Eqs. 1 and 2 for the streaming conditions are obtained on the basis of numerical calculations of the OPTTR DNDM by the Monte Carlo method. It is found that i for Eq. 1 the average momentum relaxation time in the passive region must satisfy the condition −1–2E and ii for Eq. 2 carrier penetration into the active region must occurr at a level less than 14%–15%. In the framework of such a model we have provided simple analytical expressions that estimate the low- and high-frequency limits of the generation band determined by, respectively, the average relaxation time − see Eq. 25 and the carrier penetration into the active region see Eq. 33. Having in mind that for THz radiation generation the high-frequency limit is of the most interest, for the highfrequency cutoff of the DNDM we have found that i for 3D bulk materials the relevant physical quantities are the carrier effective mass, the optical-phonon energy, and the polaroptical coupling strength; ii in passing from 3D to 2D vertical transport, for the same material the influence of 2D transport on the OPTTR is characterized entirely by the dimensionless parameter k0d related to both the radius of the optical-phonon sphere in wave-vector space k0 and the effective width of the electron localization d associated with the lowest miniband of the QW/HL structure; iii in going from 3D to 2D transport, the change of the energy dependence of the density of states is responsible for an extension of the maximum generation frequency for up to a factor of 5 times. In essence, such a model gives the “upper” estimation of the generation band limits determined primarily by the parameters of a bulk material and a 2D structure. Any other scatterings not incorporated directly into our model— namely, impurity, electron-electron, interface roughness, etc.—act mainly on the low-frequency limit since one can speak about the upper limit only in the case when an electron runaway from the regime of low-energy scatterings in the passive region takes place. Of course, the presence of additional low-energy scatterings will increase the low-frequency limit and eventually destroy the generation. Nevertheless, additional scattering mechanisms can be simply incorporated into the model by taking into account their contribution to the average momentum relaxation time in the passive region − as 1/−=1/DA+1/imp +1/ee. For example, such a procedure was used to estimate − in the experimental observation of the OPTTR generation in bulk InP.20 These estimations give relaxation times, which is reasonably close to the values estimated above.

International audience; The conditions for THz radiation generation caused by electron transite-time resonance in momentum and real spaces under low-temperature optical-phonon emission are analysed. Main attention is paid to transverse electromagnetic waves generation in: (i) 3D bulk materials and (ii) 2D quantum heterosctructures as well as (iii) longitudinal current instabilities in submicron and overmicron n+nn+ diodes. It is found that in all the cases considered the nitride-based materials and structures are the most preferable for the THz radiation generation as compared with III-V compounds. Furthermore, a considerable increase up to 5 times of the high-frequency cutoff for THz radiation generation is predicted in going from 3D to 2D transport.

International audience; We report Monte Carlo simulations of electronic noise in heavily doped nanometric GaAs Schottky-barrier diodes (SBDs) recently proposed as promising devices for THz applications. We consider a SBD operating in series with a parallel output resonant circuit when a high-frequency large-signal voltage is applied to the whole system. Significant modifications of the noise spectrum with respect to the diode subjected to a constant applied voltage are found to occur in the THz-region. To interpret such behaviour, we have developed a simple analytical approach based on the static I-V and C-V relations as well as on the series resistance of the SBD

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