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Wyświetlanie 1-15 z 37
Tytuł:
On the Mesoscopic Gate
Autorzy:
Popov, I. Yu.
Popova, S. L.
Powiązania:
https://bibliotekanauki.pl/articles/1943940.pdf
Data publikacji:
1995-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.10.-d
Opis:
The possibility of constructing of mesoscopic gate controlled by external electric field is shown.
Źródło:
Acta Physica Polonica A; 1995, 88, 6; 1113-1117
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Auger Recombination in Low-Dimensional PbSnTe Structures
Autorzy:
Mocker, M.
Lemke, F.
Powiązania:
https://bibliotekanauki.pl/articles/1879926.pdf
Data publikacji:
1991-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.10.-d
Opis:
How is the efficiency of Auger recombination in PbSnTe structures influenced by the reduction of dimensionality? Two points are investigated, the variation of matrix elements and of activation energies, respectively. It is shown that the latter one gives the more decisive effect. This effect is strongly anisotropic. Thus, {100}-planes or [100]-directions are favoured to yield large Auger lifetimes for Q2D or Q1D structures, respectively.
Źródło:
Acta Physica Polonica A; 1991, 79, 2-3; 207-212
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mechanism of Carrier Heating in High Electric Field Electroluminescence Devices
Autorzy:
Dedulewicz, S.
Godlewski, M.
Powiązania:
https://bibliotekanauki.pl/articles/1924197.pdf
Data publikacji:
1992-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.10.-d
78.60.Fi
Opis:
The mechanism of carrier heating in ZnS-based electroluminescence devices is discussed. We show that carrier acceleration by an applied electric field is at 300 K not a loss-free (ballistic carriers) process. Even for large carrier energies (about 2.5 eV) inelastic scattering on polar optical phonons dominates over elastic scattering on acoustic phonons and ionized impurities.
Źródło:
Acta Physica Polonica A; 1992, 82, 5; 865-867
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Inter-Landau Level Scattering Processes in Magnetic Field Assisted THz Quantum Cascade Laser
Autorzy:
Radovanović, J.
Daničić, A.
Milanović, V.
Indjin, D.
Ikonic, Z.
Powiązania:
https://bibliotekanauki.pl/articles/1503186.pdf
Data publikacji:
2011-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.10.-d
73.21.Fg
Opis:
We present a detailed analysis of GaAs/AlGaAs terahertz quantum cascade laser in the presence of an intense external magnetic field. One of the objectives in further development of THz quantum cascade laser is the realization of structures operating at higher temperatures. This is difficult to obtain as the operating photon emission energy is smaller than the longitudinal-optical phonon energy in the semiconductor material. With increased temperature, electrons in the upper radiative state gain sufficient in-plane energy to emit an longitudinal-optical phonon, which represents a non-radiative scattering and reduces the optical gain. By applying strong magnetic field, two-dimensional continuous energy subbands become split into series of discrete Landau levels, and at particular values of B it is possible to quench these non-radiative channels. Numerical simulations are performed on two-well design quantum cascade laser operating at 4.6 THz, implemented in GaAs/$Al_{0.15}Ga_{0.85}As$, and the magnetic field is perpendicular to the epitaxial layers. Strong oscillations of carrier lifetimes for the upper state of the laser transition, as a function of magnetic field are observed, which can be attributed to interface roughness scattering and longitudinal-optical phonon scattering between Landau levels.
Źródło:
Acta Physica Polonica A; 2011, 120, 2; 227-230
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Quantum Cascade Laser Design for Tunable Output at Characteristic Wavelengths in the Mid-Infrared Spectral Range
Autorzy:
Daničić, A.
Radovanović, J.
Milanović, V.
Indjin, D.
Ikonić, Z.
Powiązania:
https://bibliotekanauki.pl/articles/1537879.pdf
Data publikacji:
2010-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.10.-d
73.21.Fg
Opis:
We present a method for systematic optimization of quantum cascade laser active region, based on the use of the genetic algorithm. The method aims at obtaining a gain-maximized structure, designed to emit radiation at specified wavelengths suitable for direct absorption by pollutant gasses present in the ambient air. After the initial optimization stage, we introduce a strong external magnetic field to tune the laser output properties and to slightly modify the emission wavelength to match the absorption lines of additional compounds. The magnetic field is applied perpendicularly to the epitaxial layers, thus causing two-dimensional continuous energy subbands to split into series of discrete Landau levels. This affects all the relevant relaxation processes in the structure and consequently the lifetime of carriers in the upper laser level. Furthermore, strong effects of band nonparabolicity result in subtle changes of the lasing wavelength at magnetic fields which maximize the gain, thus providing a path for fine-tuning of the output radiation properties. Numerical results are presented for GaAs/$Al_{x}Ga_{1-x}As$ based quantum cascade laser structures designed to emit at particular wavelengths in the mid-infrared part of the spectrum.
Źródło:
Acta Physica Polonica A; 2010, 117, 5; 772-776
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Charge Carrier Transport in Quantum Cascade Lasers in Strong Magnetic Field
Autorzy:
Radovanović, J.
Milanović, V.
Indjin, D.
Ikonić, Z.
Harrison, P.
Powiązania:
https://bibliotekanauki.pl/articles/1505456.pdf
Data publikacji:
2011-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.10.-d
73.21.Fg
Opis:
We have developed a comprehensive rate equations based model for calculating the optical gain in the active region of a quantum cascade laser in magnetic field perpendicular to the structure layers, which takes into account all the relevant scattering channels. The model is applied to gain-optimized quantum cascade laser active region, obtained by a systematic optimization procedure based on the use of genetic algorithm, which we have previously set up for designing novel structures and improving performance of existing ones. It has proven to be very efficient in generating optimal structures which emit radiation at specified wavelengths corresponding to absorption fingerprints of particular harmful pollutants found in the atmosphere. We also illustrate another interesting prospective application of quantum cascade laser-type structures: the design of metamaterials with tunable complex permittivity, based on amplification via intersubband transitions. In this case, the role of the magnetic field is to assist the attainment of sufficient optical gain (population inversion), necessary to effectively manipulate the permittivity and fulfill the conditions for negative refraction (left-handedness).
Źródło:
Acta Physica Polonica A; 2011, 119, 2; 99-102
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Point-Contact Spectroscopy
Autorzy:
Jansen, A. G. M.
Powiązania:
https://bibliotekanauki.pl/articles/1920956.pdf
Data publikacji:
1992-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.10.-d
73.40.Jn
Opis:
In a small metallic constriction ("point contact") the transport of electrons is ballistic. The applied voltage V tunes a well-defined non-equilibrium energy eV of electrons. The nonlinear current-voltage characteristics can be used to perform energy-resolved spectroscopy of the inelastic scattering of electrons with elementary excitations in metal (e.g. phonons, magnons, crystal-field levels, paramagnetic impurities). The basic elements of the point--contact method and its applications will be discussed. In recent point-contact experiments the observed phenomena (weak localization, resistance fluctuations) need a description that goes beyond the classical Boltzmann approach of electronic transport in a point contact. In analogy to observed effects in the diffusive transport in mesoscopic systems, these phenomena are explained by considering quantum-interference effects in the ballistic transport near the contact region related to the wave character of the electrons.
Źródło:
Acta Physica Polonica A; 1992, 82, 4; 539-550
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electromagnetic Properties of Mesoscopic Cylinder
Autorzy:
Zipper, E.
Stebelski, M.
Lisowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/1968457.pdf
Data publikacji:
1997-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
72.10.-d
Opis:
The electromagnetic response of a mesoscopic cylinder made of a normal metal or a semiconductor is studied. The relation between the induced current J(q,w) and the electric field E(q,w) is derived. It is shown that the kernel K(q,w) which determines the properties of the system has a finite limit which implies infinite conductivity. The mesoscopic cylinder by virtue of its topology and small dimensions can support a persistent current. If the coherence of currents from different channels is strong enough a novel effect - the self-sustaining current can be obtained. We show that a mesoscopic multichannel system exhibits some features which bear resemblance to the superconductor.
Źródło:
Acta Physica Polonica A; 1997, 92, 5; 1087-1091
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Possible Long Time Tails in Current-Current Correlation Function for Two-Dimensional Electron Gas in Random Magnetic Field
Autorzy:
Łusakowski, A.
Turski, Ł. A.
Powiązania:
https://bibliotekanauki.pl/articles/1968462.pdf
Data publikacji:
1997-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.60.+w
72.10.-d
Opis:
We consider a two-dimensional degenerate electron gas in the presence of perpendicular random magnetic field. The magnetic field disorder which is assumed to be Gaussian is characterized by two parameters. The first is proportional to the amplitude of local magnetic field fluctuations. The second one characterizes the disorder on the longer scale - we call it the screening length. Using the Kubo formula for the conductivity we have found a class of diagrams which leads to the long time tails in the current-current correlation function. For short times in comparison with the diffusion time corresponding to the screening length this function behaves like logarithm of time, for longer times it decays like t$\text{}^{-1}$ which of course brings into question the diffusive character of the behavior of the charged particle in random magnetic field widely assumed in the literature.
Źródło:
Acta Physica Polonica A; 1997, 92, 6; 1109-1115
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Influence of Phonon Emission on Electron Transport in Hexagonal and Cubic Gallium Nitride
Autorzy:
Brazis, R.
Raguotis, R.
Powiązania:
https://bibliotekanauki.pl/articles/2041763.pdf
Data publikacji:
2005-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.10.-d
72.20.Ht
72.80.Ey
Opis:
Electron transport characteristics of GaN crystals in high electric fields are shown to be essentially influenced by different optical phonon modes inherent to the hexagonal and cubic phases of these compound crystals. Additional optical phonon modes (≈26 meV) competing with the higher-energy ones (≈92 meV) in hexagonal GaN, together with the low-lying satellite valley (Γ$\text{}_{3}$), dramatically reduce the drift mobility of electrons in comparison with conventional models. Presented Monte Carlo data are in excellent agreement with the time-of-flight experiment. The cubic GaN crystal phase with its satellite electron energy valleys shifted well above the main (Γ$\text{}_{1}$) valley is chosen as a convenient medium for elucidating the role of high-energy longitudinal optical phonon accumulation. A simple efficient one-particle Monte Carlo method is proposed for an account of excess phonons. Phonon heating is shown to bring about the moderate additional reduction of the drift mobility and an increase in mean electron energy.
Źródło:
Acta Physica Polonica A; 2005, 107, 2; 324-327
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the Possibility of Spontaneous Currents in Mesoscopic Systems
Autorzy:
Zipper, E.
Szopa, M.
Wohlleben, D.
Freche, P.
Esser, M.
Powiązania:
https://bibliotekanauki.pl/articles/1929407.pdf
Data publikacji:
1993-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
72.10.-d
71.10.+x
Opis:
It is shown that a mesoscopic metallic system can exhibit a phase transition to a low temperature state with a spontaneous orbital current if it is sufficiently free of elastic defect scattering. The interaction among the electrons, which is the reason of the phase transition, is of the magnetic origin and it leads to an ordered state of the orbital magnetic moments.
Źródło:
Acta Physica Polonica A; 1993, 84, 1; 203-211
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Monte Carlo Treatment of Non-Equilibrium Processes in n-Type InSb Crystals
Autorzy:
Ašmontas, S.
Raguotis, R.
Powiązania:
https://bibliotekanauki.pl/articles/1813219.pdf
Data publikacji:
2008-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
52.65.Pp
72.10.-d
72.10.Fk
72.20.Dp
Opis:
Numerical calculation by Monte Carlo method of the dynamic behaviour of electron ensemble in n-type InSb crystals after step-like application of electric field is presented. The results show essential influence of electron density on the energy relaxation time. The effect of electron energy cooling below equilibrium temperature in compensated n-InSb is obtained numerically for the first time, which is in agreement with experimental results.
Źródło:
Acta Physica Polonica A; 2008, 113, 3; 929-932
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electrical Conductivity for the Strongly Correlated and Hybridized Hubbard Band
Autorzy:
Kosimow, R.
Borgieł, W.
Deniszczyk, J.
Powiązania:
https://bibliotekanauki.pl/articles/2013654.pdf
Data publikacji:
2000-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.10.Fd
71.27.+a
72.10.-d
72.15.-v
Opis:
The magnetic and electrical transport properties of strongly correlated Hubbard band (f-band) hybridizing with the non-correlated conduction band (c-band) was studied. The many-body model Hamiltonian was treated within the modified alloy analogy scheme and the resulting one-body problem was solved with the use of coherent potential approximation. Within the Kubo-Greenwood formalism the dc electrical conductivity for bcc magnetic system was calculated and its variation with temperature and number of electrons was examined for different values of the Coulomb and hybridization (V) coupling constants. We found that the effect of strong correlations and hybridization on the conductivity is similar to that produced by the scattering due to the s-f interaction (spin disorder resistivity).
Źródło:
Acta Physica Polonica A; 2000, 97, 5; 799-802
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ultrafast Dynamics and Quantum Transport of Electrons in Strongly Disordered Semiconductors
Autorzy:
Kalvová, A.
Velický, B.
Powiązania:
https://bibliotekanauki.pl/articles/1933801.pdf
Data publikacji:
1995-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.25.-s
72.10.-d
78.47.+p
Opis:
The new experiments on the response of electrons in semiconductors to femtosecond optical pulses call for developing adequate theoretical tools. A promising approach has been found in using the non-equilibrium Green functions approximately factorized on the basis of the so-called generalized Kadanoff-Baym ansatz. The present work investigates the validity of such approach on an example of a semiconductor with an alloy scattering, where the coherent potential approximation allows to construct the non-equilibrium Green functions directly, so that an explicit comparison with the ansatz decoupling is possible. The ansatz for the electron distribution is in this case justified as far as the quasiparticle picture for the individual electrons is appropriate.
Źródło:
Acta Physica Polonica A; 1995, 88, 4; 767-770
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Enhancement of Electron Mobility and Photoconductivity in Quantum Well $In_{0.52}Al_{0.48}As//In_{0.53}Ga_{0.47}As//In_{0.52}Al_{0.48}As$ οn InP Substrate
Autorzy:
Kulbachinskii, V.
Lunin, R.
Yuzeeva, N.
Galiev, G.
Vasilievskii, I.
Klimov, E.
Powiązania:
https://bibliotekanauki.pl/articles/1399881.pdf
Data publikacji:
2013-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.10.-d
73.21.Fg
73.63.Hs
Opis:
Isomorphic $In_{0.52}Al_{0.48}As//In_{0.53}Ga_{0.47}As//In_{0.52}Al_{0.48}As$ quantum well structure on InP substrate were grown by molecular beam epitaxy. We investigated the electron transport properties and mobility enhancement in the structures by changing of doping level, the width d of quantum well $In_{0.53}Ga_{0.47}As$ or by illumination using light with λ = 668 nm. Persistent photoconductivity was observed in all samples due to spatial separation of carriers. We used the Shubnikov-de Haas effect to analyze subband electron concentration and mobility. The maximal mobility was observed for quantum well width d = 16 nm.
Źródło:
Acta Physica Polonica A; 2013, 123, 2; 345-348
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 37

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