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Based on the results of quantum field theory and quantum electrodynamics on virtual photons as quanta of electromagnetic interaction, we discuss the interpretation of quantum indeterminacy, uncertainty relations, and physics, which determine the probabilistic statistical character of quantum phenomena. We discuss the fundamental reasons for the appearance of the Planck constant in the uncertainty relations. The results of this work may be of interest not only for the quantum field theory and elementary particle physics but for other areas of physics as well.

The possibility of developing the broadband Fourier spectrometer based on the unsteady Josephson effect in HTSC, with a frequency range including the terahertz region, is considered. A simple design of a precisely tuned point Josephson junction is developed, which allows “fitting” of its parameters immediately under cryogenic conditions. A modification of such a spectrometer for solving the problems of factorizing multidigit numbers is proposed, which is currently one of the best known motivations of works on the quantum computer development.

We present experimental results on a high-power transmission line from the broadband pulsed Ka-band gyro-TWT to the phased antenna array. The transmission line is designed to operate in a pulse-periodic regime with a pulse width of up to 250 μs, a duty factor of 8, and an average output power of up to 15 kW. Amplitude–frequency and phase–frequency characteristics of the transmission line were measured at a low power level. It is shown that the nonlinearity of the phase–frequency characteristic does not exceed ±10° in the 34 ± 0.5 GHz frequency band.

The lifetime of free photoexcited carriers in epitaxial films of “low-temperature” gallium arsenide (LT-GaAs) is determined by the pump-probe optical reflection method. The dark resistivity of LT-GaAs layers is estimated. Emission spectra of LT-GaAs photoconductive antennas are measured in the terahertz frequency region by the Fourier transform spectroscopy.

The propagation of radiation in the frequency range 0.2–0.3 THz through samples of composite materials is considered. The samples are in the form of a strip of carbon fibers stacked into tapes impregnated with epoxide resin on in the form of a block of randomly arranged quartz filaments bonded with borosilicate glass. It is shown that the results of measurements performed in the terahertz range of frequencies may be used to study the structural parameters and for the purpose of flaw detection in composite materials.

The periodical-in-voltage features of the negative differential conductance (NDC) region in the current-voltage characteristics of a high-quality GaAs/AlAs terahertz resonant-tunneling diode have been detected. The found oscillations are considered taking account of the LO-phonon excitation stimulated by tunneling of electrons through the quantum active region in the resonance nanostructure where an undoped quantum well layer is sandwiched between two undoped barrier layers. Rearrangements in the I-V characteristics of the resonant-tunneling diode as a consequence of the topological transformation of a measurement circuit from the circuit with the series resistance R s to the circuit with the shunt R p have been experimentally studied and analyzed. The revealed substantial changes in the current-voltage characteristics of the resonant-tunneling diode are discussed schematically using Kirchhoff's voltage law.

A method of measuring the power of subterahertz and terahertz radiation using resonant tunneling diodes is proposed, based on a recording of the change in their current-voltage characteristics. The possibility of extending microwave methods into this radiation band is demonstrated. It is shown that, based on such a diode, one can detect microwave radiation over a wide range of intensities of extremely high-frequency fields.

The results of the comprehensive study of LT-GaAs epitaxial structures on GaAs and Si substrates by high-energy electron diffraction, reflection anisotropy spectroscopy, atomic force microscopy, X-ray diffraction, Raman scattering, and photoluminescence methods are presented. The results obtained indicate the existence of several channels of nonequilibrium carrier recombination, which depend, in particular, on the substrate type and on the complex dependence of the concentration of structural imperfections on the used technology and growth conditions of the structures.

Current-voltage (I–V) characteristics of resonant-tunneling diode In0.53Ga0.47As/AlAs/InP structures are studied at 300 and 77 K. The peak-to-valley current ratios were determined as 22:1 and 44:1 at temperatures of 300 and 77 K, respectively, which correspond to the maximum values for InGaAs/AlAs/InP heterostructures without an additional InAs layer of a quantum subwell in their configuration.

The characteristics of the high-frequency response of single- and double-well resonant tunneling structures in a dc electric field are investigated on the basis of the numerical solution of a time-dependent Schrodinger equation with open boundary conditions. The frequency dependence of the real part of high frequency conductivity (high-frequency response) in In0.53Ga0.47As/AlAs/InP structures is analyzed in detail for various values of the dc voltage V dc in the negative differential resistance (NDR) region. It is shown that double-well three-barrier structures are promising for the design of terahertz-band oscillators. The presence of two resonant states with close energies in such structures leads to a resonant (in frequency) response whose frequency is determined by the energy difference between these levels and can be controlled by varying the parameters of the structure. It is shown that, in principle, such structures admit narrow-band amplification, tuning of the amplification frequency, and a fine control of the amplification (oscillation) frequency in a wide range of terahertz frequencies by varying a dc electric voltage applied to the structure. Starting from a certain width of the central intermediate barrier in double-well structures, one can observe a collapse of resonances, where the structure behaves like a single-well system. This phenomenon imposes a lower limit on the oscillation frequency in three-barrier resonant tunneling structures.

A unit for filtering terahertz and subterahertz electromagnetic radiation, based on using selective frequency properties of an evanescent waveguide and quasi-optical (optic-waveguide) methods for matching to the environment, are presented. The design of the filtering unit, radiated in a frequency band of 100 GHz to several terahertz, and the measurement results of the amplitude-frequency characteristics of test filters in a range of 100–700 GHz, are given. The principle of the filter construction and design allows one to obtain a sharp and predicted transmission cutoff with an insignificant attenuation in the passband and a significant suppression of low-frequency radiation in the stop region. The experimentally measured attenuation is at a level of 6–12 dB in the filter transmission band and at a level of 30–60 dB out of the transmission band; in this case, the obtained result is determined by noises of the test setup. It is shown that the theoretical attenuation value beyond the passband may reach more than 60 dB, when the frequency is only 10% smaller than the critical one. The designed filter can be used for determining and studying spectra in the subterahertz and terahertz bands, especially in the cases, which call for a sharp spectral cutoff and exclusions of long-wave radiation components.

An analysis of high-frequency properties of the resonant tunneling diode (RTD) in a strong microwave electromagnetic field showed that the high-frequency current response increasing with the microwave power significantly more rapidly saturates out in the case of classical amplification mode, than in the case of “quantum” amplification mode. This makes the “quantum” mode even more attractive in comparison with the classical mode from the viewpoint of the possibility of amplification and generation in the range of subterahertz and terahertz frequencies and offers new opportunities to advance towards these frequencies.

The properties of a high-frequency response in resonant tunneling double-well nanostructures have been considered for various energies of electrons arriving to a structure of electrons, various frequencies of the external electromagnetic field, and various features associated with the interaction of electronic states in neighboring quantum wells in double-well nanostructures. The energy filtration effect that is caused by the breaking of the symmetry of the high-frequency response in double-well nanostructures in a static electric field has been revealed. This effect leads to a sharp increase in the gain under conditions of the quantum amplification regime and opens real prospects of a significant increase in the efficiency of solid amplifying and generating devices based on resonant tunneling double-well nanostructure in the subterahertz and terahertz frequency ranges.

The conditions of the implementation of the quantum mode of microwave generation in semiconductor resonant-tunneling diode (RTD) structures were theoretically analyzed. Based on the constructed analytical model of the steady-state current and high-frequency response in symmetric RTD structures with finite barrier widths, high-frequency properties of RTDs in an external ac electric field were analyzed by numerical simulation methods. It was shown that the quantum amplification mode can appear not only in the high-frequency region of the terahertz range, but also at relatively low frequencies due to deformation of frequency dependences in a dc electric field.

The conditions of the implementation of the quantum mode of microwave generation in semiconductor resonant-tunneling diode (RTD) structures were theoretically analyzed. The high-frequency response in structures with symmetric and asymmetric barriers was analyzed by numerical simulation methods. The effect of the Fermi distribution of carriers in the near-contact region was studied. It was shown that asymmetric structures with decreased impurity concentrations (1017 cm−3) in the emitter region are optimum from the viewpoint of experimental observation of the quantum amplification mode.

Effect of significant retardation of the phase velocity in a microwave microstrip resonator has been found and utilized for detection of spatial-dispersion phenomena in superconductors, which should be pronounced when the phase velocity became less than the Fermi velocity. The effect is explained by the influence of the fine fringes of a strip near of which the high values of curvature can appear for the system of coordinates introduced to find solutions. This leads to a spatial dependence of the phase velocity on the Lame coefficients (metric coefficients) of the curvilinear system of coordinates and can decrease the velocity significantly. Comparative estimates of the spatial effects for single-crystal high- T c (YBaCuO), Nb, and Cu samples were obtained from measurements of the resonant frequency depending on a position of the sample in the field.

A technique is developed for the photoluminescence-spectroscopy characterization of resonant-tunneling structures based on a long-period GaAs/AlGaAs superlattice that can be used for quality evaluation at all the stages of fabrication, including molecular-beam epitaxy, photolithography, and annealing. Factors such as the small energy difference between the quantum confined states in wide quantum wells, which make the photoluminescence characterization of such structures more difficult are taken into account. The long-period multiquantum-well structures are promising for the development of a new kind of solid-state intersub-band-transition devices emitting the narrow band radiation in far infrared. Their potential is essentially based on the fact that the scattering and the decay of carriers in the lower quantum-confined states may or may not involve optical phonons. The technique works at both liquid-helium and room temperature. It helps one optimize the process conditions to fabricate high-quality wide-quantum-well structures with excellent uniformity and desired parameters.

Long-wavelength IR radiation was detected in a long-period superlattice with wide quantum wells under conditions of electrical injection of charge carriers into lower size-quantization subbands, which was explained by intersubband transitions. The detected radiation probably suggests that there is a strongly nonequilibrium carrier distribution in subbands, caused by the difference between scattering processes into lower subbands with and without involving optical phonons.

The time-dependent approach is applied to the description of resonant tunnelling vertical transport accompanied by LO-phonon scattering in asymmetric double-quantum-well systems both with ideal flat and large-scale disorder interfaces. The square-law dependence of dissipative resonant tunnelling rate on the value of coupling matrix element V in the structures with flat interfaces has been found to be radically different from the linear dependence tunnelling rates on V in the structures with nonhomogeneous interfaces. As a result a substantial decrease in the effective tunnelling time in the case of nonhomogeneous interfaces is exhibited in compare with the case of structures with an ideal flat interface, particularly in weakly coupled structures. The physical reasons for the diversity of the functional dependence are discussed.

The model of the paraelectric, which is close to the point of the Mott–Hubbard instability, is shown to explain the dc resistivity and Hall effect temperature behavior for high-T c superconductor metal oxides (HTSC). In the ground state the current is carried by a liquid of boson-like pairs of carriers in upper and lower Hubbard bands. The Mott–Hubbard instability corresponds to the order-of-lattice-constant length of the mean free path and results in the temperature insensitivity of Drude conductivity. Nearly linear on T resistivity results from the Curie law via the local (acting) electric field. Fermion-like carriers, temperature excited over the energy of boson-like pair dissociation (pseudo gap), explain the temperature behavior of Hall effect. Available data are compared with the model.

Transformation kinetics of the resonant-tunneling domain structure in a superlattice in a rapidly varying electric field is investigated using real-time studies of current response. It is shown that the kinetics is mainly determined by a lag in redistribution of the space charge that forms the domain boundary. A nonmonotonic oscillatory dependence of the transient-process duration on the amplitude of a voltage pulse is observed, as well as the effect of the weak dependence of the transformation time on the displacement of the domain boundary, which indicates that the transformation processes is discrete. Possibilities for controlling the switching processes in a multistable system of current states in weakly coupled semiconductor superlattices are discussed.

The dynamics of the switching between multistable current branches in weakly coupled GaAs/AlGaAs superlattices was investigated. A multilevel logic device with several stable current states was proposed and the possibility of switching between any selected states by voltage pulses of appropriate amplitude and polarity was demonstrated.

The fabrication of diamond-like coating on high- T c superconductors is investigated. Carbon thin films were deposited on YBa 2 Cu 3 O 7 single-crystal film by pulse-laser sputtering of graphite targets. Deposition at room temperature yields diamond-like films with high optical transmission, high resistivity, and good adhesion to unpretreated YBa 2 Cu 3 O 7 . Degradation of superconducting properties or deterioration of mechanical characteristics of YBa 2 Cu 3 O 7 films was not observed after carbon deposition and subsequent low temperature thermocycling. The water-protective properties of these diamond-like coatings were investigated.

The possibility of intersubband population inversion and the necessary conditions for its achievement in wide quantum well structures with the energy space between the lowest states being lower than the optical phonon energy are considered. Two possible designs are proposed, both using resonant tunnelling for selective depopulation of the lowest subband. The analysis of resonance tunnelling times and intersubband relaxation rates due to various scattering processes is carried out, demonstrating the possibility, at sufficiently low carrier concentrations, of inverted carrier distributions over the lowest subbands under optical pumping or electrical injecting conditions.

Theoretical estimates and the results of vertical transport and optical investigations in GaAs/AlGaAs structures show that resonant tunneling can lead efficiently to selective depopulation of the levels, resulting in a population inversion and possible stimulated emission due to intersubband transitions between the lowest states in wide-quantum-well structures.

The model of the paraelectric, which is close to the point of the Mott–Hubbard instability, is shown to explain the dc resistivity and Hall effect temperature behaviour for high- T c superconductor metal oxides (HTSC). In the ground state, the current is carried by a liquid of boson-like pairs of carriers in upper and lower Hubbard bands. The Mott–Hubbard instability corresponds to the order-of-lattice-constant length of the mean free path and results in the temperature insensitivity of Drude conductivity. Nearly linear on T resistivity results from the Curie law via the local (acting) electric field. Fermion-like carriers, temperature excited over the energy of boson-like pair dissociation (pseudo gap), explain the temperature behaviour of Hall effect. Available data are compared with the model.

Current–voltage characteristics of 30 period 390 A GaAs/110 A Al0,3Ga0,7As superlattices are studied. Features revealed in multistable current branches of the hysteresis loops made it possible to estimate gradual changes in the size and shape of the domain boundary and reconstruct the final shape of the domain boundary. It was concluded that a considerable current bistability observed in the investigated superlattices is due to the domain boundary expansion. Switching between bistable current states in each hysteresis loop is detected. The switching time depends on the direction of the current jump. The switching time from a high- to low-current state is about 10−7 s; the time of the reverse switching to the high-current state is about 10−6 s. The observed switching is attributed to the shrinkage and expansion of the domain boundary size.

The model of the paraelectric, which is close to the point of the Mott–Hubbard instability, is shown to explain the DC resistivity and Hall effect temperature behaviour for high- T c superconductor metal oxides (HTSC). In the ground state the current is carried by a liquid of boson-like pairs of carriers in upper and lower Hubbard bands. The Mott–Hubbard instability corresponds to the order-of-lattice-constant length of the mean free path and results in the temperature insensitivity of Drude conductivity. Nearly linear on T resistivity results from the Curie law via the local (acting) electric field. Fermion-like carriers, temperature excited over the energy of boson-like pair dissociation (pseudogap), explain the temperature behaviour of Hall effect. Available data are compared with the model.

For high–Tc superconductor metal oxides (HTSC) it is shown that the dc resistivity and Hall effect temperature behaviour can be explained by the model of the paraelectric material close to the point of the Mott-Hubbard instability, in the ground state of which the current is carried by a liquid of boson-like pairs of carriers in upper and lower Hubbard bands. The Mott-Hubbard instability corresponds to the order-of-lattice-constant length of the mean free path and results in the temperature insensitivity of Drude conductivity. Nearly linear on T resistivity results from the Curie law via the local (acting) electric field. Fermion-like carriers, temperature excited over the energy of boson-like pair dissociation (pseudo gap), explain the temperature behaviour of Hall effect. Available data are compared with the model.

Development of physical principles of THz-wave amplification and oscillation is one of problems determining progress in modern solid state electronics towards high frequencies and ultrahigh performance. Novel perspectives are tied with use of resonant tunneling quantum effects, characterized by transient times less than 1 ps, comparable with fast response of superconducting devices. The information about these properties can be obtained from investigation of high-frequency oscillations or current-voltage switching phenomena in resonant-tunneling (RTD) nanostructures. In the paper the results of theoretical and experimental studies of high-frequency properties of RTD elements in subterahertz and terahertz frequency range are presented basing on developed theory of high-frequency response in RTD as well as on experimental high-frequency investigation data and current-voltage switching phenomena investigation results of effects correspondingly related to stationary current characteristics changes in single-quantum-well as well as in doublequantum- well resonant-tunneling diode nanostructures under external electromagnetic electrical field.

It is shown that under resonance tunneling conditions the energy structure of electric-field domains in doped superlattices is substantially different from a resonance structure. As the impurity concentration decreases, the domain walls become wider and the current hysteresis becomes narrower (collapses) as a result of the mismatch of the resonance levels in the region of a domain wall. A physical interpretation of the criterion for the existence of electric-field domains is given.

Diamond-like carbon coatings were prepared by pulsed laser ablation of a graphite target in a high-vacuum (~10 −6 Torr) environment on Si, SiO 2 and single-crystal YBa 2 Cu 3 O 7 film substrates. Investigations by a variety of spectroscopic techniques demonstrate that the films had a high density (~2.9 g cm −3 ) close to that of diamond, a high ratio of sp 3 to sp 2 bonding (0.75/0.25), and IR transparency. The films were hard, adhesive to the substrate and had a high resistivity. The parameters of the growth process that allows production of DLC films with high water-resistance properties on YBa 2 Cu 3 O 7 substrates have been determined.

The possibility of fabrication of diamond-like coating on high- T c superconductors is investigated. Carbon thin films were deposited on single-crystal YBa 2 Cu 3 O 7 film substrates by pulsed-laser sputtering of graphite targets. Deposition at room temperature yields diamond-like films with high optical transmission, high resistivity, and good adhesion to unpretreated substrates. Degradation of superconducting properties or deterioration of mechanical characteristics of YBa 2 Cu 3 O 7 films was not observed after carbon deposition and subsequent low-temperature thermocycling. The water-protective properties of these diamond-like coatings were investigated.

To improve the quality factor Q of a microwave resonator by damping the intermode coupling we have studied the influence of the dispersion properties on the loss characteristics of the superconducting microstrip-like resonator. The electromagnetic field was intentionally disturbed in the region of transmission lines outside the resonator to damp modes selectively using short-circuiting stubs on input and output microstrip lines. It is found that spectrum of resonances includes parasitic modes, the energy of which is concentrated mainly in the region of connecting microstrip lines. Interaction of the main mode with parasitic ones significantly reduces the highest Q value of the main operating mode. Damping of parasitic modes enables to improve Q from less than 103 to order of 105.

A transverse (in-plane) magnetic field (B = 0–7 T) was used to modify the shape of the tunnelling resonance between electronic states in neighbouring quantum wells of a superlattice and to investigate the effect of the modification of the tunnelling resonance profile on electric field domain stability and self-sustained current oscillations effect in GaAs/AlGaAs superlattices.

The results of experimental and theoretical studies of hole distribution function and cyclotron resonance (CR) laser emission processes in uniaxially stressed p-Ge in strong crossed E ⊥ H fields are presented. The CR emission spectra were studied for various orientations of E and H fields with respect to the crystallographic axes of the p-Ge crystal. A complicated structure of CR emission spectra (instead of a single line without stress) was found to arise in stressed crystals, corresponding to transitions between different pairs of light hole Landau levels. A considerable effect of quantum deformation of the lower light hole Landau levels due to interaction and mixing of light and heavy hole states on emission spectra was found, resulting in strong broadening and shift with the stress of an emission line, corresponding to (n = 2) → (n = 1) transitions. The transitions were shown to dominate in CR emission spectra for stress larger than 400 bar. Numerical calculations of hole lifetimes and distribution function in uniaxially stressed Ge based on the quantum model of carrier dynamics in strong crossed E and H fields were carried out, taking into account the optical phonon and ionized impurity scattering processes. The results of the calculations allowed us to identify the observed CR transitions.

THz detection by plasma wave mechanism in InGaAs HEMTs is studied in high/quantizing magnetic fields regime. The correlation between the photovoltaic response and magnetoresistance is revealed. It allows to explain the nature of strong oscillations observed in the transistor Terahertz photoresponse.

International audience; Terahertz (THz) detection by plasma wave mechanism in InGaAs field effect transistors is studied in high/quantizing magnetic fields regime. The correlation between the photovoltaic response and magnetoresistance is revealed. It allows explaining the dominant physical mechanism responsible for strong oscillations observed in the transistor THz photoresponse. The results indicate also a serious discrepancy between experimental data and existing theoretical model. (C) 2010 American Institute of Physics.

The light hole cyclotron stimulated emission in p-Ge in strong E perpendicular to H fields was studied as a function of E and H field orientation and uniaxial stress applied to the crystal. Quantum model calculations of light hole scattering rates and Landau level population are used to interpret the results. The low frequency part of the intersubband emission spectra was investigated, and new emission lines were found. The role of impurity transitions in stimulated emission processes is discussed.

Possible approaches to improvement of quality of a high-speed planar transmission line are investigated by systematic study of superconductor high- Q microstrip resonators in the frequency range of order 10 GHz. Superconductor microstrip resonators with maximal highest quality-factors Q >10 5 were constructed. Relative contributions of spectral (geometrical and non-dissipative material properties), on one hand, and of dissipative (losses in materials) characteristics, on another hand, into the limitation of maximal achievable values of the quality of microstrip resonators are investigated. It is shown that the highest by now Q ≥10 5 are limited dominantly by the spectral properties of microstrip resonators.

The hole dynamics and emission processes in degenerate band semiconductors in strong crossedE ⊥B fields were studied both theoretically and experimentally. The Luttinger effective mass Hamiltonian was used to study the Landau level energy spectrum in anisotropic valence bands of Ge. The dependence of the energy spectrum onE,H fields orientation is analysed. The role of quantum effects, such as interaction and mixing of light and heavy hole states in the scattering process and Landau level population is studied. The results of experimental studies of stimulated emission spectra for intersub-band and cyclotron transitions as well as their dependence onE,H field orientation are presented, the experimental data being in good agreement with the quantum model calculations.

The results of investigation of cyclotron type stimulated emission processes inp-Ge in strong crossedE ⊥B fields are presented. Using the optimumE,B field orientation the spectral range of continuous tuning of the emission line frequency was increased substantially. A tunable sub-millimetre laser with the tuning rangev = 25 to 95cm−1 (λ = 105 to 400μm), output power 10 to 100mW and emission linewidthδv ⩽ 0.2cm−1 is described.

A time‐dependent approach is applied to the problem of dissipative resonant electron tunneling in asymmetric double‐quantum‐well systems both with ideal flat and large‐scale disorder interfaces. An electron tunneling rate associated with LO‐phonon scattering and the average effective tunneling time are calculated. The square‐law dependence of dissipative resonant tunneling rate on the value of coupling matrix element V in the structures with flat interfaces has been found to be radically different from the linear dependence tunneling rates on V in the structures with nonhomogeneous interfaces. As a result there is a substantial increase in the effective tunneling time in structures with an ideal flat interface in comparison with nonhomogeneous interfaces, particularly in weakly coupled structures. The physical reasons for the diversity of the functional dependence are discussed.

Multi quantum-well long-period structures are promising for a number of important applications including the far infrared intersubband-transition-based narrow-band radiation devices, microwave resonant-tunneling and self-sustained current oscillation generators, multilevel-logic element devices based on the recently found switching effect between the multistable current states, terahertz emission detectors. All devices have in common the operation dependence on resonant-tunneling rearrangement effects in the long-period structure. We present the results of optical investigation of resonant-tunneling rearrangement processes in long-period GaAs/AlGaAs superlattice structures under application of vertical electric field by means of low-temperature photoluminescence (PL) technique in comparisons with the data of vertical transport measurements performed simultaneously on the same structures. The effect of appearance of the new PL peaks accompanied by suppression of the old ones with increasing bias voltage has been detected, resulting from the Stark shift phenomenon. PL intensity dependences on the applied voltage are presented for the first time which complement the measured current-voltage data. The transition effect from bound (exciton) to free (electron and hole) states in electric field is observed. It is shown that the optical research method can be more sensitive in some situations to provide the crucial information about the resonant-tunneling rearrangement effects even under condition when the ordinary current-voltage measurements do not reveal any features.

Local electric fields in the metal oxide superconductors, which are generally close to the metal‐insulator phase transition and possess the very short length of the mean free path for current carriers, order of a lattice constant, can result in the paraelectric permittivity for bound charges (soft dipoles), which obeys the Curie law. The Hall effect and dc resistivity temperature behaviours are explained here by the model of the paraelectric crystal close to the point of the Mott‐Hubbard instability, in the ground state of which the current is carried by a liquid of boson‐like pairs of carriers in upper and lower Hubbard bands. Fermion‐like carriers, temperature excited over the energy of boson‐like pair dissociation (pseudo gap), explain the temperature behaviour of Hall effect. Available data are compared with the model.

Photoluminescence technique is developed for characterization of resonant-tunneling diode structures formed of the GaAs/AlGaAs long-period superlattices in process of fabrication, which allows to estimate quality of the fabricated structure after the main stages of the technological process, including the MBE growth of multi-layer structure, lithography and annealing. The long-period multiquantum-well structures are promising for development of a new kind of solid-state intersubband-transition devices emitting the narrow band radiation in far infrared. This PL technique permits the corrections of the technology parameters to grow the structures with required properties and high homogeneity and can be used at room temperature as well as at low temperature.

High-frequency response properties of single and double-quan- tum-well resonant tunneling diodes (RTD) are examined in a wide fre- quency range, up to terahertz (THz) frequencies, on the base of proposed quantum theory. Numerical solutions of time-dependent Schrodinger equations with open-system boundary conditions in an exter- nal electromagnetic field are performed. The numerical solutions take into account the influence of bias DC voltage on electronic states in RTD with finite height and width of barriers both for monoenergetic and for Fermi- distributed electrons in emitter and collector parts of structures. We show that the presence of an additional level in double-quantum-well structures breaks the response symmetry and leads to selective narrow-band fre- quency amplification, as well as to the effect of amplification frequency tuning at THz frequencies by variation of applied bias voltage. These phe- nomena predict an increase of gain coefficient and open new perspectives for engineering of novel types of THz oscillators and other high-frequency units. © 2013 Society of Photo-Optical Instrumentation Engineers (SPIE). (DOI: 10.1117/1.OE .52.1.014002)

In studying the microwave (10 GHz) response of both single crystal and ceramic samples of the YBa 2 Cu 3 O 7 in Nb resonator we have found dielectric permittivity dependent strongly on wave-vector resulting in appearance of the new dielectric resonances with hysteretic temperature behaviour. Data show the importance of the non-conducting “bound” electron polarization in strong local fields and spatial dispersion, which lead to the polariton-like interaction between microwaves and electrons in a high-T c superconductor. The effects of the polariton-like microwave excitations on the limiting mechanisms in superconducting cavities are discussed.