The development of the double selective doping technique has stimulated interest in the optical properties of semiconductor nanostructures containing the H‒-similar impurity centers and their molecular complexes. Interest in the optical properties of quantum dots with the D_2^ - centers in an electric field is due, first of all, to the possibility of effective control of both the binding energy of impurity states and the photoexcitation spectra of molecular impurities. Depending on the quantum dot radius and the spatial configuration of impurity molecules, the D_2^ - photoexcitation band can be in the visible, IR, or terahertz frequency range, which significantly expands the range of instrumental applications of quantum dots with impurity states. Therefore, great interest is presented by quasi-zero-dimensional structures with the D_2^ - impurity states, which can be used to create IR and terahertz receivers. The aim of this study is to theoretically investigate the features of the spectra of intracenter optical transitions in quasi-zero-dimensional structures with the D_2^ - centers in an electric field. The binding energy of the D_2^ - states has been calculated by the zero-radius potential method in the effective mass approximation. The expression for the coefficient of impurity absorption of light has been obtained in the dipole approximation within the perturbation theory. It has been shown that the violation of symmetry in the arrangement of the D^0 centers leads to the removal of degeneracy between the g and u terms. It is shown that an external electric field leads to a decrease in the splitting between the g- and u-terms. It has been established that the photoexcitation spectrum is a band the position of which depends on the external electric-field strength. The quasi-zero-dimensional structures with the D_2^ - centers in an external electric field can be used to create IR and terahertz detectors with controllable characteristics.

The aim of this work is to experimentally investigate the features of the formation of Au nanoparticles (NPs) in SiO 2 –TiO 2 films by the method of local electrochemical reduction using an atomic force microscope (AFM) probe. The study has the additional aim of establishing the modes of the formation of Au NPs, which provide controlled production of NPs with specified parameters. The created scientific and technical products are intended for use in nanoelectronics, integrated optics, optoelectronics, and plasmonics to create new nanoelectronic devices based on MNP arrays embedded in dielectric films, metal nanoantennas of arbitrary shape embedded in optical dielectric waveguides based on thin-film structures, etc. (The relevance of ongoing research is related to this.) An experimental study of the formation processes of individual Au NPs in the thickness of SiO 2 –TiO 2 films has been carried out by the method of local electrochemical reduction of Au(III) ions using an AFM probe. Au NPs have been formed in SiO 2 –TiO 2 films using a SolverPro atomic force microscope manufactured by Nanotechnology-MDT (Zelenograd, Russia) in the contact mode. We have used AFM cantilevers made of Si with Pt coating by Nanotechnology-MDT CSG-01. Before the formation of Au NPs, AFM images of a selected area of the gel-film surface have been measured: z ( x , y ), where x and y are the coordinates of the AFM probe tip in the sample surface plane and z is the surface height at the point with coordinates x , y . In addition, simultaneously with AFM images, images of current for selected areas of the sample surface have been measured. The processes of the Au NPs formation in SiO 2 –TiO 2 gel films containing Au(III) ions deposited on glass substrates with an ITO sublayer by the sol–gel method, have been studied in the course of local electrochemical reduction of Au(III) ions using a conducting AFM probe. It is shown that, after the modification of gel films by applying positive voltage pulses to the AFM probe relative to the ITO sublayer, the images of current for the modified regions show channels of current associated with the formation of Au NPs at the interface between the ITO sublayer and of the gel film as a result of local electrochemical reduction of Au(III) in the area under the contact of the AFM probe to the surface of the gel film. It has been established that the formation of Au NPs also manifests itself in the appearance of hysteresis in the cyclic CVC of the contact between the AFM probe and the surface of the gel film measured during the formation of NPs. It was found that, upon modification of the SiO 2 –TiO 2 gel film by applying a negative voltage pulse to the AFM probe relative to the ITO sublayer, the formation of toroidal Au nanostructures has been observed, associated with the electrochemical reduction of Au(III) ions near the contact of the AFM probe with the surface of the gel film. The results of the carried out studies are planned to be used in the future in the development of methods for the controlled formation of MNPs in thin dielectric films using AFM.

The influence of temperature on the processes of dissipative electron tunneling through individual Co nanoparticles (NPs) in an HfO 2 film (10 nm thick) on a conductive substrate with a Co sublayer has been experimentally studied by atomic force microscopy (AFM) with a conducting probe. Co NPs were formed by local anodic oxidation of the Co sublayer using an AFM probe with subsequent drift of Co ions to the AFM probe, their reduction, and growth of Co NPs near the contact of the AFM probe tip with the HfO 2 film surface. In the experiment, the tunnel current–voltage characteristics (CVC) of the formed Co NPs were measured when voltage was applied between the AFM probe and the Co sublayer at different temperatures in the range of 20–105°С. The experimental results were interpreted on the basis of the theory of one-dimensional dissipative tunneling for a model double-well oscillatory potential in an external electric field. At one of the voltage polarities on the AFM probe, kinks in I–V characteristics were observed, accompanied by current oscillations through the AFM probe I , which, according to the theory, corresponds to the situation when the initially asymmetric double-well potential becomes symmetrical. The amplitude of the mentioned oscillations Δ I falls slightly non-linearly with increasing temperature. The results of the experiment were compared with the results of calculations of the temperature dependence of the maximum amplitude of oscillations on the field dependence of the probability of 1D dissipative tunneling. The obtained qualitative agreement between the experimental 19 and theoretical temperature dependences indicates that the experimentally observed features of I–V characteristics are associated with the effect of macroscopic quantum tunneling with dissipation. A qualitative agreement was obtained between the experimental and theoretical results that allow us to assume the possibility of experimental observation of the macroscopic dissipative tunneling effects [1] and thereby confirm the hypothesis expressed in the groundbreaking works of A.J. Leggett, A.I. Larkin, Yu.N. Ovchinnikov, and other authors.

Quantum dots (QDs) have unique optical properties that are widely used in optoelectronics, biology, and medicine. The problem of controlling the spectral and luminescent properties of QDs has initiated studies of the mechanisms by which QDs interact with each other and with the surrounding matrix. Such interactions can, under certain conditions, significantly modify the radiative properties of QDs, which will affect the characteristics of laser structures and biosensors based on them. The aim of this work is a theoretical study of the 2D dissipative tunneling effect in the “QD–surrounding matrix” system, as well as the pair electrostatic interaction of QDs with A + + e impurity complexes, on recombination radiation associated with the optical transition of an electron from the QD ground state to the quasi-stationary A + state in an external electric field. The interaction of an electron, which is in the ground state of a QD, and a hole that is localized at the A + center has been considered within the framework of the adiabatic approximation. The dispersion equations that determine dependence of the hole binding energy in the A + + e impurity complex in a spherically symmetric QD on the external electric field and dissipative tunneling parameters have been obtained within the zero range potential model, in the effective mass approximation. Calculation of the spectral intensity of recombination radiation (SIRR) in QDs with an A + +e impurity complex in an external electric field has been performed in the dipole approximation. Influence of the electric field on the ground state of an electron in a QD has been taken into account in the second order of the perturbation theory. Numerical calculations and plotting were carried out for a semiconductor quantum dot based on InSb using the symbolic mathematics of Mathcad 14 and Wolfram Mathematica 9. The 2D dissipative tunneling probability has been calculated with exponential accuracy for the 2D oscillatory potential model at a finite temperature, taking into account the linear interaction with the phonon modes of the environment media (or a heat bath) in the one-instanton semiclassical approximation. It is shown that the field dependence of the binding energy for the quasi-stationary A + state has an oscillating character, associated with quantum beats that occur during parallel 2D tunneling transfer. It is found that the SIRR curves have a characteristic kink corresponding to the 2D bifurcation point that occurs when the tunneling regimes in the interacting pair of QDs change from synchronous to asynchronous. It has been established that, in the vicinity of the 2D bifurcation point, there are irregular oscillations in the SIRR associated with the modes of quantum beats, in the course of which competing trajectories of tunneling appear. It is found that the parameters of dissipative tunneling—the temperature, frequency of the phonon mode, constant of interaction with the contact medium, constant of the QDs interaction—have a significant effect on the amplitude of quantum beats and the position of the 2D bifurcation point in the SIRR. Taking into account the interaction of the QD with the surrounding matrix leads to a significant modification of the SIRR, which manifests itself in the form of bifurcation points and quantum beats that depend on the dissipative tunneling parameters. Accounting for the pairwise interaction of QDs with each other via hole repulsion in A + + e complexes leads to suppression of recombination radiation with an increase in the interaction constant.

At present, much attention is paid to the dielectric engineering of the material of the surrounding matrix and low-dimensional structures, which makes it possible to purposefully change their properties and optimize the characteristics of semiconductor devices. The aim of this work is a theoretical study of the influence of the pair interaction of quantum dots (QDs), as well as their interaction with the surrounding matrix through 2D dissipative tunneling, on the photodielectric effect (PDE) associated with the excitation of an impurity complex A + + e in a QD system in an external electric field. Interaction of an electron with a hole in an impurity complex A + + e in a QD has been considered in the adiabatic approximation. The dispersion equations for a hole in an impurity complex A + + e in the presence of an external electric field and 2D dissipative tunneling for the s - and p -states of an electron in a QD are obtained within the framework of the zero-range potential model in the effective mass approximation. The influence of the electric field on the ground state of an electron in a QD has been taken into account in the second order of the perturbation theory. The probability of 2D dissipative tunneling is calculated in the one-instanton semiclassical approximation. The relative change in dielectric permittivity has been calculated in the dipole approximation. PDE field-dependence curves have been plotted for InSb QDs. It is shown that the PDE field dependence at a certain value of the strength of an external electric field and the parameters of 2D dissipative tunneling has a characteristic kink associated with the effect of 2D bifurcation, when, under the action of an electric field, the double-well oscillatory potential simulating the “QD–surrounding matrix” system is transformed and the tunnel transfer mode changes from synchronous to asynchronous. It has been established that there are irregular oscillations on the PDE curves in the vicinity of the 2D bifurcation point, which are associated with the regime of quantum beats. It is shown that the amplitude of the oscillations increases with increasing phonon mode frequency and temperature, while the break point shifts towards weaker fields. It has been found that an increase in the constant of interaction with the contact medium, as well as with the constant of the pair interaction of QDs, leads to the suppression of the PDE.

The modern physics of condensed matter, chemistry, and biology deal with quite a large number of systems that are modeled by 1D and 2D oscillatory double-well potentials of variable topology, the parameters of which can change in an external electric field. In solving quantum problems, an exact analytical solution of the Schrödinger equation can only be obtained for a limited number of models (a well with infinite walls, a quantum oscillator, a hydrogen atom, a cubic parabola potential, a double-well oscillator, and some others). When studying a double-well oscillator potential, which simulates the low-temperature chemical kinetics, tunneling transport in structures with quantum dots (QDs) and quantum molecules and another analytical solution to the Schrödinger equation can only be found under the zero temperature condition and the assumption of the absent interaction of tunneling particles with a medium‒thermostat matrix. If these parameters are taken into account, the Schrödinger equation cannot be solved analytically within the conventional quantum-mechanical approach. In the semiclassical approximation (when the de Broglie wavelength of a tunneling particle is significantly shorter than the subbarrier length), using the instanton method, one can analytically determine the tunneling probability. This was first done by the pioneers of the science of quantum tunneling with dissipation: Acad. of the Russian Academy of Sciences A.I. Larkin, Prof. Yu.N. Ovchinnikov (Landau Institute for Theoretical Physics, Russian Academy of Sciences), and winner of the Nobel Prize in Physics (2003) Prof. A.J. Leggett et al. when modeling Josephson contacts with a cubic parabola potential [1, 2, 11]. A.A. Ovchinnikov, Yu.I. Dakhnovsky, and M.B. Semenov [11] were the first to obtain an analytical solution for a 1D double-well oscillatory potential within this theory when modeling low-temperature chemical reactions as tunnel systems with dissipation.

Background. Semiconductor quantum dots, due to their unique optical properties, are a promising material for creating optoelectronic devices. At the same time, the devices’ parameters change significantly over a wide temperature range, which requires knowledge of the temperature dependence of both the band structure and the energy of impurity levels in quantum dots. In this case, the electron-phonon interaction acts as the most important mechanism for the temperature shift of energy levels. The purpose of this work is to theoretically study the effect of electron-phonon interaction on the temperature dependence of radiative recombination in an extrinsic complex ( A+ + e ) in a semiconductor quasi-zerodimensional structure. Materials and methods. The theoretical consideration of the temperature effect on the energy levels in a semiconductor quantum dot was carried out by a statistical method under the assumption that the main contribution to the temperature dependence comes from the electron-phonon interaction. The dispersion equation, which determines the binding energy of a hole in an extrinsic complex ( A+ + e ) in a spherically symmetric quantum dot, was obtained in the framework of the adiabatic approximation in the model of a zero-radius potential. The calculation of the spectral intensity of recombination radiation in a quasi-zero-dimensional structure with extrinsic complex ( A+ + e ) was performed in the dipole approximation taking into account the dispersion of the radius of quantum dots. The temperature dependence curves are plotted for the case of InSb-based quantum dots. Results. The temperature dependence of the binding energy in the complex ( A+ + e ) is calculated for various values of the quantum dot radius. It is shown that, with increasing temperature, the hole binding energy decreases, which is associated with the temperature “spreading” of the wave function of the quasistationary A+ -state under conditions of electron-phonon and hole-phonon interactions. It was found that with a decrease in the radius of a quantum dot, the binding energy of the A+ -state increases due to an increase in the energy of the ground state of the adiabatic potential of an electron. The dependence of the spectral intensity of the recombination radiation on the transition energy is calculated for various values of temperature. It was found that with increasing temperature, the threshold transition energy shifts to the short-wavelength region of the spectrum, and temperature quenching of the recombination radiation takes placeThis is due to a decrease in the overlap integral of the wave functions of the initial and final states of an electron due to an increase in the transition energy. Conclusions. The effect of electron-phonon interaction on recombination processes in extrinsic complexes ( A+ + e ) in a spherically symmetric quantum dot manifests itself in temperature reduction of the spectral intensity of the recombination radiation. The effect of reaching a “plateau” appears to be common to different photoluminescence mechanisms.

We report the results of experimental studies of the photoelectric properties of a p–i–n GaAs photodiode with InAs/GaAs(001) double asymmetric quantum dots (DAQDs) grown by self-assembling in the metal–organic vapor-phase epitaxy process. Three peaks were observed in the dependence of the photocurrent on the reverse bias measured at monochromatic photoexcitation of the DAQDs at the wavelength corresponding to the energy of interband optical transitions between the ground hole and electron states in the larger quantum dots (QDs). These peaks were related to the tunneling of the photoexcited electrons between the QDs, including a dissipative one (with emission and absorption of optical phonons). The experimental results agree qualitatively with the theoretical field dependence of the probability of 1D dissipative tunneling between QDs.

Semiconductor quantum dots, due to their unique optical properties, are promising materials for the design of optoelectronic devices. At the same time, the parameters of instruments significantly depend both on the band structure and the impurity energy levels in quantum dots. In this regard, the electron–phonon interaction acts as the most important mechanism of temperature shift in energy levels. The aim of the present work was to theoretically study how the electron–phonon interaction influences the temperature dependence of radiative recombination in an impurity A^ + + e complex in a semiconductor quasi-zero-dimensional structure. The effect of temperature on the energy levels in a semiconductor quantum dot was theoretically considered by the statistics method assuming that the electron–phonon interaction makes the main contribution to the temperature dependence. The dispersion equation defining the hole binding energy in the impurity A^ + + e complex in a spherically symmetric quantum dot was obtained in terms of the adiabatic approximation in the zero-range potential model. The spectral intensity of recombination radiation in the quasi-zero-dimensional structure with impurity A^ + + e complexes was calculated in the dipole approximation taking into account the radius dispersion of quantum dots. Temperature curves were plotted for the case of InSb-based quantum dots. The temperature dependence of the binding energy in the A^ + + e complex was calculated for different values of the quantum-dot radius. The hole binding energy was shown to decrease with an increase in temperature, which was due to a temperature spreading of the wave function of a quasi-steady A + state under the conditions of electron–phonon and hole–phonon interactions. The bond energy of the A + state was found to increase with a decrease in the quantum-dot radius due to an increase in the ground state energy of the adiabatic electron potential. The spectral intensity of recombination radiation was calculated as a function of the transition energy for different temperature values. It was found that, with an increase in temperature, the threshold transition energy shifts to the short-wave spectral region and thermal quenching of the recombination radiation occurs. This was due to a decrease in the overlap integral of the wave functions of initial and final electron states because of the transition energy increase. The effect of the electron–phonon interaction on recombination processes in the impurity A^ + + e complex in spherically symmetric quantum dot is manifested in temperature quenching of the recombination radiation spectral intensity. The effect of coming to a plateau appears to be common for different mechanisms of photoluminescence.

Interest in the optical properties of quantum dots (QDs) with the A^ + + e impurity complexes is due to the possibility of construction of new elements of semiconductor optoelectronics based on such structures. Relatively high sensitivity of the band structure and energy of impurity states in QDs to an external electric field opens up prospects for control of the spectra of recombination radiation with the aid of impurity centers. The purpose of this work is to theoretically study the effect of external electric field on radiative recombination in the A^ + + e impurity complex in semiconductor QDs. The spectral intensity of recombination radiation (SIRR) in a quantum dot with the A^ + + e impurity complexes in the presence of external electric field is calculated in the dipole approximation. The effect of the electric field on the ground state of electron in a QD is taken into account in the second order of the perturbation theory. The SIRR spectral curves and the dependences of the SIRR on the strength of the external electric field are plotted for QDs based on InSb. The SIRR is calculated in the dipole approximation with allowance for the Lorentz broadening of energy levels in QD with the A^ + + e impurity complex. The calculation is based on the use of the adiabatic approximation in the analysis of the interaction of a hole localized at the A+ center with an electron localized on the ground state of the QD. It is shown that a significant variation in the SIRR is caused by a decrease in the overlap integral of the wave functions of electron and hole localized at the A+ center due to the electron–hole polarization. It is also shown that the asymmetry of the position of the minimum of the adiabatic potential in the presence of electric field leads to a nontrivial dependence of the SIRR on the coordinates of the A+ center: when the impurity center approaches the boundary of the QD, the SIRR maximum is blue-shifted, and an increase in the electric field strength leads to a significant decrease in the radiation intensity and a red shift of its maximum (quantum-size Stark effect). In the presence of electric field, the SIRR can efficiently be controlled with the aid of the A^ + + e impurity complexes due to the modification of the electron adiabatic potential.

The interest in studying the optical and electrical properties of nanotubes is caused by their specific features, such as the band gap, which is dependent on the nanotube structure symmetry, and high electrical conductivity, due to which they can be considered as promising materials for nanoelectronics. Most existing methods of preparation of these structures suggest the formation of nanotubes in the form of arrays, with a large dispersion of their characteristic sizes. Therefore, the most important problem is to analyze the influence of size dispersion on the optical properties of a nanotube bundle. The purpose of this study is to theoretically investigate the influence of dispersion of the spiral-nanotube radius on macroscopic quantum effects arising at anisotropic transfer of the photon momentum to the electron subsystem. The model under consideration is a cylindrical nanotube with infinitely thin walls. The nanotube spiral symmetry is described by extended spiral perturbation simulated by the δ potential. The emf of photon drag and emf arising due to Joule heating of the electron system are calculated in the quadrupole approximation with allowance for the dispersion of nanotube radii. The influence of dispersion of the characteristic spiral-nanotube sizes on macroscopic quantum effects in a longitudinal magnetic field is theoretically studied. Analytical formulas are derived (with allowance for the dispersion of the characteristic sizes of spiral nanotubes in an array) for the photon-drag emf in a standing electromagnetic wave and for the emf due to Joule heating of the electron system by the photon-drag current of electrons through a nanotube in a longitudinal magnetic field. The influence of the dispersion of characteristic sizes of spiral nanotubes in an array on the macroscopic quantum effects is investigated. It is shown that the macroscopic quantum effect, which is related to the photon-drag emf in a standing electromagnetic wave, may be suppressed in real arrays of nanotubes, where the dispersion of their radii plays a significant role. It is also shown that suppression of the emf, related to Joule heating of the electron system by the photon-drag current through a nanotube, increases with an increase in the standard deviation, which is due to significant dispersion of the characteristic spiral-nanotube radii.

Impurities of different chemical elements inevitably emerge during the preparation of semiconductor nanostructures or are intentionally added to change their transport and optical properties. Most impurities in a bound state can have two or more electrons, rather than one electron. In this case, interelectronic correlations enabling the double photoionization of an impurity atom, one of fundamental reactions, start to play an important role. The aim of the present work was to calculate the first ionization potential of a two-electron impurity center in a semiconductor quantum well by the variation method, as well as to theoretically study the effect of correlations on the double photoionization spectra of two-electron impurity centers in a multiwell quantum structure. The bond energy and first ionization potential of a two-electron atom were calculated by the variation method where the second ionization potential was taken as an empirical parameter. The expression for the impurity light absorption coefficient was obtained in the dipole approximation taking into account the quantum-well width variance. The zero-radius potential method was generalized to the case of two-electron impurities with zero effective nuclear charge in semiconductor quantum wells. An analytical expression for the first ionization potential of a two-electron impurity center was obtained by the variation method in terms of the semiempirical model. The impurity light absorption coefficient upon the one-photon photoionization of a two-electron impurity in a multiwell quantum structure was calculated in the dipole approximation. It is shown that, due to the spatial restriction in a quantum well in one direction, electronic correlations are enhanced to result in higher threshold values of the second ionization potential than those in quantum dots and, as a consequence, more rigid existence conditions of two-electron impurity states. Also, a decrease in the quantum size effect and an increase in the electronic correlation in multiwell quantum structures compared to quasi-zero-dimensional structures were shown to result in transformation of the absorption curve, which is expressed in an increase in the dip between peaks in the double-humped spectral curve.

There has been an increasing interest in the study of the effect of electric field on the properties of semiconductor quantum dots. This is due to the fact that such systems provide a high degree of freedom in the control of the band structure and the binding energy of impurity states, which is important for instrumental applications. Of particular interest is the study of the effect of electric field on the A(+) impurity states, which can form long-lived A(+) + e complexes with nonequilibrium electrons. Variations in the magnitude of the external electric field can be used to control the binding energy of the A(+) state, concentration of charge carriers, and optical properties of quasi-zero-dimensional structures. The purpose of this work is to theoretically study the effect of external electric field on the binding energy of a hole in the A(+) + e impurity complex in a spherically symmetric quantum dot. The interaction of an electron in the ground state of a quantum dot and a hole localized at the A(+) center is considered in the framework of the adiabatic approximation. The dispersion relation that determines the dependence of the binding energy of a hole in the A(+) + e impurity complex in a spherically symmetric quantum dot on the magnitude of the external electric field is obtained in the model of the zero-radius potential in the approximation of effective mass. All curves are plotted for quantum dots based on InSb. An analytical solution of the problem of bound states of a hole in the A(+) + e complex in a spherically symmetric quantum dot is obtained in the presence of an external electric field in the zeroradius-potential model in the adiabatic approximation. The centered and uncentered locations of the A(+) center in a quantum dot are considered. It is shown that the curve of the field dependence of the binding energy of the A(+) center has a characteristic maximum, the position of which is related to the dynamics of the adiabatic potential in the presence of an external electric field. It is shown that there is a threshold value of the external electric field at which the existence of the bound A(+) state becomes impossible. The monotonic behavior of the dependence of the binding energy of the A(+) state on the radius of the QD is violated for the uncentered A(+) center. For certain values of the QD radius, the binding energy reaches maximum, which is due to coincidence of the position of the center and the minimum of the adiabatic potential.

We report on the results of experimental studies of the photoelectric properties of a GaAs p-i-n photodiode with InAs/GaAs(001) double asymmetric quantum dots (DAQDs) grown by self-assembling in Metal Organic Vapor Phase Epitaxy (MOVPE) process. Three peaks were observed in the dependence of the photocurrent on the reverse bias measured at monochromatic photoexcitation of the DAQDs at the wavelength corresponding to the energy of interband optical transitions between the ground hole and electron states in the bigger QDs. These peaks were related to the tunneling of the photoexcited electrons between the QDs including the dissipative one (with emission and absorption of the optical phonons). The experimental results agree qualitatively with the theoretical field dependence of the 1D dissipative tunneling probability between the QDs.

Temperature dependence of the spectral intensity of recombination radiation in a quasi-zero-dimensional structure, containing impurity complexes "A + + e" (a hole localized on a neutral acceptor, interacting with an electron localized in the ground state of a quantum dot), has been investigated in an external electric field in the presence of tunneling decay of a quasistationary A + -state.Probability of dissipative tunneling of a hole has been calculated in the one-instanton approximation, and the influence of tunneling decay and of an external electric field on the A + -state binding energy and on the spectra of recombination radiation, associated with the optical transition of an electron from the ground state of a quantum dot to the A + -state of the impurity center, has been investigated in the adiabatic approximation."Dips" in the temperature dependence of the SIRR have been revealed, which are associated with the presence of resonant tunneling at certain values of temperature and strength of the external electric field, for which the double-well oscillatory potential becomes symmetric.

We report on the results of experimental studies of the photocurrent (PC) of photodiodes based on GaAs p-i-n structures with InAs/GaAs(001) double asymmetric quantum dot (DAQD) arrays obtained by self-assembling in the process of low-pressure metal-organic vapor phase epitaxy (LP-MOVPE). Three peaks were observed in the dependence of the PC on the reverse bias, measured under photoexcitation with a photon energy equal to the energy of the interband ground state transition in larger InAs QDs. These peaks were attributed to photoexcitation of electrons from the ground hole states in larger QDs into the ground electron states followed by resonant dissipative (with absorption or emission of optical phonons) and conservative tunneling into the GaAs conduction band via the ground electron states in smaller QDs. The PC dependence on the bias voltage agrees qualitatively with the theoretical field dependence of the probability of 1D dissipative tunneling between the QDs.

Abstract. In framework of the 2D - dissipative tunneling theory in approximation of a rarefied gas of the «instanton - antiinstanton pairs» at a finite temperature under the conditions of an external electric field, the features of tunneling transport for planar structures with quantum dots (QDs) from colloidal gold, that have metamaterial properties, have been studied. It was experimentally shown that, depending on the positioning of the cantilever needle of a combined atomic force and scanning tunneling microscope (AFM / STM), either above a single quantum dot or between two neighboring quantum dots, either a single or double effect of 2D tunneling bifurcations have been observed, respectively. It is such a double bifurcation regime, as our theoretical model has shown, that is associated with the manifestation of the metamaterial properties by the structure under study. A convincing qualitative agreement between the experimental I – V characteristics and the field dependence of the 2D - dissipative tunneling probability in the two studied modes, taking into account the observed quantum beats in the vicinity of the 2D bifurcation points, has been obtained.

Within the 2D theory of dissipative tunneling in the semiclassical approximation (a rarefied gas of instanton–anti-instanton pairs) at a finite temperature in the presence of an external electric field, the features of tunneling transport in the planar structures with the quantum dots made of colloidal gold—which, presumably, possess the properties of a metamaterial—are investigated. It is shown experimentally that either a single effect or a double effect of 2D tunnel bifurcations (in the form of a kink or kinks on the tunneling current–voltage curve) is observed depending on the position of the cantilever tip of a combined atomic force and scanning tunneling microscope (AFM/STM), which can be either above a single quantum dot or between two adjacent quantum dots, respectively. As our theoretical model shows, such a regime of double bifurcation (a double smoothed kink on the tunneling current–voltage curve) that is associated with the manifestation of the properties of a metamaterial by the structure under study. A convincing qualitative agreement is obtained between the experimental current–voltage characteristics and the field dependence of the probability of 2D dissipative tunneling in the two investigated regimes with due regard for the observed quantum beats (oscillations) in the vicinity of 2D bifurcation points.

In the zero-range potential model and in the effective mass approximation, dispersion equations have been obtained, that describe dependence of the average binding energies of the quasistationary g- and u-states of the D-2(-) center in the QD, as well as the widths of energy levels on the magnitude of the external electric field and the parameters of 1D-dissipative tunneling. Dips in the field dependences of the binding energies average values for quasi-stationary g- and u-states have been revealed. It is shown that the field dependences of the energy level widths for the g- and u- states of the Dz -center have a resonance structure at the external electric field strengths corresponding to the dips in the field dependences of the average binding energies. In the dipole approximation, the field dependence of the probability of the electron radiative transition from a quasistationary u-state to a quasi-stationary g-state of the D-2(-)-center in a QD in the presence of dissipative tunneling with the participation of two local phonon modes has been calculated. It was found that the curve of the radiative transition probability (RTP) dependence on the strength of the external electric field contains three peaks.

A brief review of articles developing the quantum tunneling with dissipation theory, as well as its applications to various problems in condensed matter physics, in particular, quantum mesoscopy of nanostructures, has been presented. A generalization of the instanton method to the case of impurity quasistationary states in quantum molecules described in the model of a double-well oscillatory potential has been also considered. The flexibility of the instanton method is demonstrated, which allows, in combination with the physics of low-dimensional systems, to obtain the solution of problems on the optical and transport properties of quantum molecules with impurity quasistationary states in an analytical form, as well as to take into account the effect of external fields. Part I of the article is presented in № 1 for 2017.