The study of GaAs/AlAs terahertz resonant tunneling diodes demonstrates the competition of self-excitation and amplification processes incorporating the terahertz-range polaritons. The effects of the magnitude of the resonant peak current and low current in the valley of the current-voltage characteristic are demonstrated taking into account the general laws of detection in the mode of internal amplification in the region of negative differential conductivity.
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 Rs to the circuit with the shunt Rp 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.
The characteristics of high performance signal detection over a wide frequency range (1 MHz ÷ 100 GHz) in the context of a non-standard application for tunnel diodes is discusses.
In the context of all-weather tracking distant cosmic objects issues, six original schemes of detecting far-infrared radiation are presented here, which approach in their sensitivity to the level that allows their use in photon counting mode. The first one is a modernized version of the Up-converter (with the placement of nonlinear crystal/mixer inside of resonator in a single laser unit) for the transfer of far-infrared photons in the visible range, where the photon counting is possible via PMT or APD. The second scheme of registration far IR is based on the forward bias LED at a current, which is still not enough for the generation of radiation. The experiments allowed to observe photoresponse of such a system for the red border of the internal photoelectric effect. The following three schemes are cryogenic. And the last one is an Up-converter, where instead of the classical mixing on nonlinear crystal is used quantum effect of releasing energy metastable state under the influence of the far-infrared radiation quanta.
Conducting media with the spatial dispersion may be described formally by a singly operator – an operator of a dielectric permittivity, which completely defines a microwave response of conductors with the spatial dispersion. So the eigenvalue problem for the permittivity operator of conductors and superconductors possessing a strong spatial dispersion at low temperatures is of a great importance since the corresponding solutions are the stable waves for the constitutive equation in a self-consistent microwave field. Here a wave problem is formulated to search the solutions, which correspond to the eigenvalues of a permittivity operator, similar to the relationship and the general solutions are obtained. A significant role of the spatial-type conjugated. Dispersion relationship and general solutions are obtained. A significant role of the spatial-type force resonances is considered. Conditions for the spatial resonances are derived. The obtained resonances include particular solutions corresponding to the related to a polarization, two of which correspond to waves with an amplitude increasing into the depth of a conductor, and two else describes solutions with unusual properties.
In view of high-speed application of microwave transmission lines the coherent quantum effects in conducting components of transmission lines were considered. When a characteristic coherence length of the electronic wave functions becomes to be comparable with a length of the transmission line, such quantum effects make it necessary to consider the line as a “quantum” transmission line. We discuss a kind of such quantum effects related to the Einstein- Podolsky-Rosen paradox and analyze their influence on the properties of transmission lines and a possibility to increase a speed of signal transmission by using these quantum properties. Brief review of alternatives and phenomena related to the problem of Einstein-Podolsky-Rosen paradox is presented. On the example of the magnetic perturbation traveling in a closed superconducting microwave slotline the features of the quantum-mechanical reaction of this completely coherent macroscopic system in response to the local impact excitation of its part is considered. The transient processes are analyzed in the context of the Einstein-Rosen-Podolsky paradox.
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.
Various variants of use high-sensitivity superconducting quantum interferometers (SQUID) in
problems closely connected with development of a quantum computer are considered. 1.Hardware realization
of a method of definition of midget concentration of the paramagnetic centers, based on measurement of their
magnetization SQUID in a mode of modulation microwave saturation of magnetic sublevels is offered. The
method will allow make testing of semi-conductor materials necessary for creation of a spin solid-state
quantum computer. 2.The opportunity of application SQUID for reading a condition of the quantum register,
based on the quantum-statistical mechanism, allowing registered a state of single spin, is considered. 3.The
circuit super low noise the quantum electrometer, based on use SQUID is offered as a measuring instrument
of magnetization of spin system in which exchange interaction is adjusted by potential on in parallel
connected managing electrodes (on type a spin ensemble computer).
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.
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.
Raman scattering and anti-Stokes photoluminescence spectra of the crystalline GaP, ZnSe and ZnTe are investigated at room and liquid helium temperatures. The increase of quality-factor of vibrational modes and sharpening of polariton band are found in the Raman spectrum at liquid- helium temperature in a frequency range, corresponding to the TO and LO vibrations. A tentative explanation of the observed anti-Stokes photoluminescence is given with a help of the deep-level state analysis of these materials. The low-temperature anti-Stokes photoluminescence is found to be a common property of the wide gap semiconductors and can probe the spatial distribution profiles of impurities in these crystals.
Spectra of the Raman scattering (RS) by transverse and longitudinal A1-vibrations in crystals of the lithium niobate and lithium tantalate are investigated at room and liquid helium temperatures. An essential decrease of the RS- linewidths for scattering by A1T-phonons is found in the course of deceasing from room to liquid helium temperature. The obtained results show that coherent excitation of polariton modes in ferroelectrics is a promising method for generating the frequency-tunable submillimeter-band radiation.
Raman scattering (RS) spectra of the crystalline (alpha) - sulphur are investigated at room and liquid helium temperatures. The doublets and quartets are found in the RS- spectrum at helium temperature in a frequency range, corresponding to the intramolecular vibrations. An explanation of the observed splitting is given with a help of the group theory analysis of intramolecular vibrations, affected by the crystalline field. The shifts of the spectral position of characteristic peaks in the RS-spectrum of the (alpha) -sulphur are measured with the temperature variation.
Microwave oscillations have been observed for the first time from the spacer-cladded GaAs/AlAs multiple-quantum-well resonant tunneling structures stabilized by a microstrip resonator system, which is compatible with use of MBE technology methods, provides a proper circuit conditions at high frequencies appearing to be rather promising for applications in millimeter and submillimeter wavelength range.
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