共查询到20条相似文献,搜索用时 31 毫秒
1.
A. G. Milekhin Yu. A. Pusep Yu. A. Yanovskii V. V. Preobrazhenskii B. R. Semyagin D. I. Lubyshev 《JETP Letters》1996,64(5):393-397
The vibrational spectrum of short-period GaSb/AlSb superlattices in the frequency range of GaSb optical phonons is investigated
in detail. Localization of transverse GaSb optical phonons in GaSb/AlSb superlattices is observed experimentally for the first
time. The dispersions of TO and LO phonons in GaSb are measured.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 5, 361–364 (10 September 1996) 相似文献
2.
Additive contributions to the Seebeck and Peltier coefficients made by nonequilibrium longitudinal optical phonons have been
calculated. The results obtained are valid for any temperature and applicable to polar nondegenerate semiconductors with low
carrier concentrations. The calculated components of the thermoelectric coefficients are exponentially small in the low-temperature
domain and reach a maximum at k
BT∼ħω
0. In materials with a large carrier mass and strong electron-phonon coupling the contribution of optical phonons to the Seebeck
coefficient can exceed 1 mV/K.
Fiz. Tverd. Tela (St. Petersburg) 40, 1209–1215 (July 1998) 相似文献
3.
V. A. Volodin M. D. Efremov V. Ya. Prints V. V. Preobrazhenskii B. R. Semyagin 《JETP Letters》1996,63(12):994-999
The localization of longitudinal optical phonons in GaAs/AlAs lateral superlattices and quantum wires grown on faceted GaAs
(311)A surfaces are investigated by means of Raman scattering spectroscopy. The frequencies of the localized phonons are found
to decrease as the average thickness of the GaAs layer is decreased from 21 to 15 Å. As the GaAs thickness is decreased further
to 11.3 and 8.5 Å, the frequencies of the localized phonons increases sharply in connection with the formation of an array
of quantum wires. The frequencies calculated in a two-dimensional chain model agree with the experimental values. This makes
it possible to interpret the increase in the frequencies of localized phonon states as being the result of the quantization
of phonons in the array of one-dimensional objects. The results obtained support the model of GaAs (311)A surface faceting
with a facet height of 10.2 Å.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 12, 942–946 (25 June 1996) 相似文献
4.
V. E. Zhitomirskii O. V. Volkov I. V. Kukushkin S. Rozhko W. Dietsche 《JETP Letters》1999,69(1):31-37
The effect of absorption of nonequilibrium acoustical phonons on the intensity of recombination of a two-dimensional electron
gas in a magnetic field is investigated. The nonequilibrium acoustical phonons are emitted in the relaxation of electrons
in a tunnel junction deposited on the back side of a sample with a two-dimensional electronic channel. It is demonstrated
that the optical signal showing the intensity of the recombination of nonequilibrium electrons from a photoexcited size-quantization
subband can serve as a sensitive detector of acoustical phonons. Because the general heating of two-dimensional carriers and
the intersubband transitions stimulated by the absorption of nonequilibrium acoustical phonons lead to effects of different
sign, the useful signal can be discriminated unambiguously.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 1, 30–35 (10 January 1999) 相似文献
5.
A. A. Verevkin N. G. Ptitsina K. V. Smirnov G. N. Gol’tsman E. M. Gershenzon K. S. Ingvesson 《JETP Letters》1996,64(5):404-409
The temperature dependence of the energy relaxation time τe (T) of a two-dimensional electron gas at an AlGaAs/GaAs heterointerface is measured under quasiequilibrium conditions in the
region of the transition from scattering by acoustic phonons to scattering with the participation of optical phonons. The
temperature interval of constant τe, where scattering by the deformation potential predominates, is determined. In the preceding, low-temperature region, where
piezoacoustic and deformation-potential-induced scattering processes coexist, τ e decreases slowly with increasing temperature. Optical phonons start to participate in the scattering processes at T∼25 K (the characteristic phonon lifetime was equal to τLOτ4.5 ps). The energy losses calculated from the τe data in a model with an effective nonequilibrium electron temperature agree with the published data obtained under strong
heating conditions.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 5, 371–375 (10 September 1996) 相似文献
6.
Raman scattering of light by optical phonons in Si-Ge-Si structures with pseudomorphic germanium quantum dots has been investigated.
Resonance amplification of the scattering intensity on E
0 (Γ7−Γ8) transitions has been observed. It is shown that as a result of the formation of the layer of germanium quantum dots, the
resonance energy is ∼0.3 eV higher than in the two-dimensional case.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 3, 203–207 (10 August 1996) 相似文献
7.
Thermoelectric power in quasi-two-dimensional systems with scattering of current carriers by phonons
B. M. Askerov B. I. Guliev S. R. Figarova I. R. Gadirova 《Physics of the Solid State》1997,39(10):1659-1660
The thermopower α in electron systems with a quasi-two-dimensional energy spectrum is investigated in the relaxation-time tensor approximation.
The longitudinal and transverse components of the thermopower are calculated for scattering of the current carriers by different
types of phonons. It is shown that the anisotropy of the thermopower in such systems is substantial. The dependence of a on
the ratio of the Fermi level ɛ
F to the half-width ɛ
0 of the one-dimensional conduction band is considered. For scattering by acoustical and nonpolar optical phonons, the thermopower
changes sign: α becomes positive for ɛ
F<ɛ
0. Comparison of the theory with published experimental data demonstrates good qualitative agreement.
Fiz. Tverd. Tela (St. Petersburg) 39, 1857–1858 (October 1997) 相似文献
8.
B. Kh. Bairamov A. V. Gol’tsev V. V. Toporov R. T. Phillips R. Laiho K. Dettmer 《Physics of the Solid State》1998,40(5):864-866
The results of a theoretical and experimental investigation of resonant Mandelstam-Brillouin light scattering by thermal acoustic
phonons with k=0 near the direct absorption edge (in the case of ZnSe crystals) are analyzed. The appearance of a new type of resonant increase
in the intensity of Raman scattering by optical phonons with k≠0, which corresponds to resonance with the scattered light in the output channel, near the indirect absorption edge (in the
case of semi-insulating GaP:N crystals) is also reported. The resonant gain reaches ∼4×103 at frequencies corresponding to overtone scattering assisted by LO(X) and LO(L) phonons. Exciton states belonging to both discrete exciton bands and to the continuous spectrum are considered as the intermediate
states involved in the scattering processes in calculations of the resonant scattering tensors. In addition, all the intraband
transitions, as well as the interband transitions between the conduction band, the valence bands, and the spin-orbit split-off
band are taken into account, and good agreement with the experimental results is obtained.
Fiz. Tverd. Tela (St. Petersburg) 40, 938–940 (May 1998) 相似文献
9.
L. E. Vorob’ev D. V. Donetskii D. A. Firsov E. B. Bondarenko G. G. Zegrya E. Towe 《JETP Letters》1998,67(7):533-538
Terahertz emission accompanying heating of two-dimensional electrons by a strong electric field applied along size-quantized
GaAs/AlGaAs layers is observed and investigated. The emission is due to indirect optical transitions of hot electrons in the
bottom size-quantization band. The experimentally obtained emission spectra are compared with the spectra calculated taking
into account scattering of electrons by optical phonons, impurities, and interfacial roughness and electron-electron scattering.
Satisfactory agreement is obtained. The temperature of the hot electrons is determined from a comparison of the spectra.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 7, 507–511 (10 April 1998) 相似文献
10.
L. A. Falkovsky 《JETP Letters》1997,66(12):860-867
Inelastic (Raman) light scattering by phonons interacting with anisotropic imperfections is investigated. Three different
kind of disorder-induced defects (point, linear and planar) have been considered. The optical phonon width and line shape
are found to depend importantly on the dimension of the imperfections. There is a close correspondence between the scale of
the imperfection and the phonon line shape observed in the Raman scattering experiments. The dependence of the phonon frequency
shift and width on the defect concentrations is calculated, and the critical concentrations at which the optical phonon can
no longer be observed are determined.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 12, 817–822 (25 December 1997)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
11.
An investigation is reported of stimulated two-photon emission by Bose-condensed excitons accompanied by a coherent two-exciton
recombination, i.e., by simultaneous recombination of two excitons with opposite momenta leaving unchanged the occupation
numbers of exciton states with momenta p≠0. Raman light scattering (RLS) accompanied by a similar two-exciton recombination (or production of two excitons) is also
analyzed. The processes under consideration can occur only if a system contains Bose condensate, so their detection can be
used as a new method to reveal Bose condensation of excitons. The recoil momentum, which corresponds to a change in the momentum
of the electromagnetic field in the processes, is transferred to phonons or impurities. If the recoil momentum is transmitted
to optical phonons with frequency ω
0
s
, whose occupation numbers are negligible, and the incident light frequency satisfies ω<2Ω, where Ω_=Ω−ω
0
s
is the difference frequency and Ω is the light frequency corresponding to the recombination of an exciton with zero momentum,
stimulated two-photon emission and RLS with coherent two-exciton recombination give rise to a line at 2Ω_ −ω and an anti-Stokes component at ω+2Ω_, respectively. For ω2Ω_ the RLS spectrum contains Stokes and anti-Stokes components at frequencies ω±2Ω_, whereas stimulated two-photon emission is impossible. Formulas for the cross sections at finite temperatures are obtained
for the processes under consideration. Our estimates indicate that a spectral line at 2Ω_−ω, corresponding to the stimulated two-photon emission accompanied by coherent optical phonon-assisted two-exciton recombination
can be experimentally detected in Cu2O.
Zh. éksp. Teor. Fiz. 115, 1353–1376 (April 1999) 相似文献
12.
The optical vibrational modes in GaAs/AlAs structures grown on a (311)A-oriented GaAs surface are investigated. It is found that the line corresponding to the fundamental TO vibrational mode localized in a GaAs quantum wire is split into two lines with different directions of the polarization vector.
The dispersion of the TO phonons of GaAs in the (311) direction is determined from the IR spectra of periodic structures.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 2, 107–110 (25 January 1998) 相似文献
13.
V. A. Margulis 《Journal of Experimental and Theoretical Physics》1997,84(3):603-611
The coefficient of absorption of electromagnetic radiation by a quasi-two-dimensional electron gas placed in an oblique magnetic
field is found. The scattering of electrons by optical phonons is shown to lead to resonant absorption. The shape of the resonance
peaks on the absorption curve is studied, and their doublet nature is demonstrated. Finally, the dependence of the resonance
peaks on the angle between the magnetic field vector and the confinement plane is investigated.
Zh. éksp. Teor. Fiz. 111, 1092–1106 (March 1997) 相似文献
14.
L. I. Korovin I. G. Lang S. T. Pavlov 《Journal of Experimental and Theoretical Physics》1997,84(6):1197-1208
The spatial correlation of light-generated electrons and holes in a quasi-two-dimensional electron gas in a strong magnetic
field is investigated in an approximation linear in the intensity of the exciting light. The correlation is due to the interaction
of the electrons and holes with longitudinal optical (LO) phonons. The theory permits calculating, on the basis of a special diagrammatic technique, two distribution functions of
an electron-hole pair with respect to the distance between the electron and the hole after the emission of N phonons: first, the function determining the total number of pairs which have emitted N phonons and, second, the function related to the rank-4 light-scattering tensor in interband resonance Raman scattering of
light. A special feature of the system is that the electron and hole energy levels are discrete. The calculation is performed
for a square quantum well with infinitely high barriers. The distribution function and the total number of electron-hole pairs
before the emission of phonons as well as the distribution function corresponding to two-phonon resonance Raman scattering
are calculated. The theory predicts the appearance of several close-lying peaks in the excitation spectrum under resonance
conditions. The number of peaks is related to the number of the Landau level participating in the optical transition. The
distance between peaks is determined by the electron-phonon coupling constant. Far from resonance there is one peak, which
is much weaker than the peaks obtained under resonance conditions.
Zh. éksp. Teor. Fiz. 111, 2194–2214 (June 1997) 相似文献
15.
It is observed experimentally that in the low-frequency Raman light scattering spectrum of amorphous porous silicon the boson
peak situated in the acoustic range is more sensitive to the structural order than the optical mode presently used to determine
the degree of disorder. It is shown that this is because, unlike the coefficient of interaction with optical vibrations, the
coefficient of interaction between light and acoustic vibrations contains an additional factor, the square of the reciprocal
correlation length of the vibrational excitations, i.e., the intensity of light scattering by acoustic phonons has an additional
dependence on the degree of disorder.
Zh. éksp. Teor. Fiz. 114, 315–321 (July 1998) 相似文献
16.
A model is proposed for explaining the anomalous behavior of the far-IR absorption spectra of the dielectric Van Vleck paramagnet
thulium ethyl sulfate TmES. The good agreement obtained between the calculations and experiment on the basis of the idea of
a resonance interaction between Tm3+ ions in one of the excited doublet states and optical phonons gives grounds for asserting that coupled 4f-electron-phonon excitations exist in TmES single crystals in high magnetic fields at liquid-helium temperatures.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 12, 983–987 (25 June 1998) 相似文献
17.
A. Milekhin Yu. Pusep Yu. Yanovskii V. Preobrazhenskii B. Semyagin 《Physics of the Solid State》1998,40(3):507-509
A study is reported of optical vibrational modes in [311]-grown GaAs/AlAs superlattices. An analysis of the TO and LO localized modes observed in IR reflectance spectra showed that the difference between the TO and LO mode frequencies in superlattices grown on (311)A and (311)B surfaces is due to the different localization lengths of these modes. The dispersion of transverse optical phonons in GaAs
derived from IR reflectance spectra is in a good agreement with Raman scattering data.
Fiz. Tverd. Tela (St. Petersburg) 40, 550–552 (March 1998) 相似文献
18.
L. E. Vorob’ev 《JETP Letters》1998,68(5):417-425
A mechanism is proposed for obtaining intraband population inversion of electrons in size-quantization levels through the
injection of electron-hole pairs into the i region of a heterostructure with quantum wells or quantum dots. Key elements of the mechanism are the simultaneous generation
of interband (hv≈E
g
) near-IR radiation and the presence of a “metastable” level. In quantum wells such a level can be produced by making use
of the weak overlap of the wave functions of electrons in the levels of a quantum well of complicated configuration and exploiting
the characteristic features of the interaction of electrons with optical phonons in polar semiconductors. In quantum dots
such a level forms as a result of the phonon bottleneck effect. Estimates are made of the gain for mid-IR radiation in intraband
optical transitions of electrons.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 5, 392–399 (10 September 1998) 相似文献
19.
We have observed additional lines, shifted in both directions relative to the frequency of the bulk phonon of Ge, in the Raman
scattering spectra from optical phonons in germanium quantum dots. The observed phonon modes are shown to be due to the straining
of the quantum dots as a result of the lattice mismatch of the Ge and Si matrices. The observed frequency shifts, with allowance
for optical-phonon localization effects, make it possible to determine the sizes of the regions with different strain states
in the quantum dots.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 4, 279–283 (25 August 1999) 相似文献
20.
Abstract Summary The 30 kbar high pressure unit for low temperatures and the digital processing have been applied to the tunneling investigations of Ge and GaAs. The obtained results include the values of the mode Gruneisen constants for zone boundary phonons in <100> direction in Ge, the irregular optical phonons behavior in GaAs, the bistability of tunneling voltage-current curve for GaAs at elevated pressure and the observation of optically induced oscillations on the tunneling conductance of GaAs Schottky barrier. The semi-quantitative model involving the conductance band structure change under pressure and DX-centers in GaAs(Te) is used for the tentative explanation. 相似文献