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1.
We present a discussion of resonant Raman scattering by optical phonons at the E1 energy gap of group IV and groups III–V compound semiconductor crystals (e.g., Ge and InSb). For allowed scattering by TO and LO phonons, the q-dependent “double resonant” two-band calculation of the Raman tensor may display destructive interference effects when the intermediate electron-hole pairs are uncorrelated. We also discuss the Franz-Keldysh mechanism of resonant electric field induced Raman scattering by LO phonons. The double resonance terms due to this mechanism will, for large electric fields, broaden and have its largest resonance enhancement at the energy gap. 相似文献
2.
The dependence of the width of the spectral function of electrons and holes on the wavevector and excitation energy in a 2D
electron system with spin-orbit interaction caused by structural inversion asymmetry is analyzed in the G
0
W
0 approximation. It is shown that an additional (relative to the generation of electron-hole pairs) channel of hole decay due
to emission of a plasmon appears in the case of low electron density. Noticeable spin asymmetry of the spectral function width
appears in the region of electron excitations. 相似文献
3.
Resonant Raman scattering in AgBr single crystals is studied at low temperatures. Excitation in resonance with the indirectΓ — L exciton as intermediate state gives rise to selectively enhanced narrow two-phonon Raman scattering. The phonons involved are pairs ofLA andTO phonons of opposite wavevectors near theL-point. A simple model involving one discrete exciton level is developed to explain the resonance behaviour. The temperature dependence of the scattered intensity, that is studied for 1.8 K <T < 35 K, can consistently be interpreted within this model as being due to the lifetime of the intermediate state. Assuming that the excitons predominantly decay by one-phonon scattering with long wavelength acoustical phonons the predicted temperature dependence of the intensity is found in good agreement with the experimental result. Additional scattering peaks are believed to be due to third-order processes involving an acousticalX-phonon in addition to theL-phonons of the second-order scattering. Using an oriented sample the resonant Raman peaks are found to be polarized. 相似文献
4.
Optical-resonance-Raman scattering by acoustic phonons is used to study the effect of an electric field on the state of excitons
in GaAs/AlAs superlattices. When the energy of the exciting photon coincides with the energy of an exciton bound to Wannier-Stark
states of a heavy hole and electron with Δn=0,±1, the acoustic Raman scattering is enhanced. Oscillations in the intensity of the Raman spectrum in the electric field
are explained by resonance delocalization of the exciton ground state as it interacts with Wannier-Stark states of neighboring
quantum wells or with Wannier-Stark states of a higher electron miniband.
Fiz. Tverd. Tela (St. Petersburg) 40, 827–829 (May 1998) 相似文献
5.
Y. Kuramoto 《Zeitschrift für Physik B Condensed Matter》1979,35(3):233-243
A theory is developed on giant quantum attenuation of ultrasound in bismuth. The present theory successfully explains the following experimental results in strong magnetic fields (H 100 kG): (i) When two attenuation peaks, the one due do electrons and the other due to holes, coincide as a function of magnetic field, the attenuation is exceptionally large at temperatures around 1 K and decreases rapidly with increasing temperatures; (ii) on the contrary, an isolated attenuation peak shows only a weak temperature dependence; (iii) the line shape of an isolated hole peak is highly asymmetric. The theory includes both intraband and interband impurity scatterings, acoustic phonon scattering, and takes account of Coulomb correlation effects via electron-electron, hole-hole and electron-hole two-body distribution functions. As a result, the electron-hole attractive correlation is found to play a crucial role in making the large attenuation mentioned in (i). For (ii), the electron-hole correlation is ineffective because of the large difference in Fermi velocities, and the acoustic phonon scattering is found to be important. Finally, the result (iii) is attributed to the small density of states of the reservoir Landau subbands in the strong magnetic field regime. The present theory assumes no phase transition to account for the result (i) in contrast to previous theories. 相似文献
6.
A short high-power pulse of ionizing radiation creates a high concentration of nonequilibrium electrons and holes in a dielectric.
They quickly lose their energy, generating a multiplicity of secondary quasiparticles: electron—hole pairs, excitons, plasmons,
phonons of all types, and others. When the kinetic energy of an electron becomes less that some value EΔ≈(1.3-2)Eg it loses the ability to perform collisional ionization and electron excitations of the dielectric medium. Such an electron
is said to be ionization-passive. It relaxes to the bottom of the lower conduction band by emitting phonons. Similarly a hole
becomes ionization-passive when it “floats up” above some level EH and loses the ability for Auger ionization of the dielectric medium. It continues to float upward to the ceiling of the upper
valance band only by emitting phonons. The concentrations of ionization-passive electrons and holes are larger by several
orders of magnitude than those of the active electrons and holes and consequently make of a far larger contribution to many
kinetic processes such as luminescence. Intraband and interband quantum transitions make the greatest contribution to the
fundamental (independent of impurities and intrinsic defects) electromagnetic radiation of ionization-passive electrons and
holes. Consequently the brightest types of purely fundamental luminescence of strongly nonequilibrium electrons and holes
are intraband and interband luminescence. These forms of luminescence, discovered relatively recently, carry valuable information
on the high-energy states of the electrons in the conduction band and of the holes in the valence band of a dielectric. Experimental
investigations of these types of luminescence were made, mainly on alkali halide crystals which were excited by nanoseconal
pulses of high-current-density electrons and by two-photon absorption of the ultraviolet harmonics of pulsed laser radiation
beams of nanosecond and picosecond duration. The present article gives the results of theoretical calculations of the spectra
and other characteristics of intraband electron and interband hole luminescence which are compared with the experimental data.
Institute of High-Current Electronics, Sibrian Branch of the Russian Academy of Sciences, Polytechnic University, Tomsk. Translated
from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 13–41, November, 1997. 相似文献
7.
T. N. Zavaritskaya I. V. Kucherenko N. N. Mel’nik G. Karczewski M. L. Skorikov 《Physics of the Solid State》2013,55(11):2355-2360
Photoluminescence and Raman scattering spectra in CdTe/ZnTe heterostructures and superlattices with narrow quantum wells (4.8–9.2 Å) in a temperature range of 5–300 K have been measured. The temperature dependences of the intensity of exciton luminescence in isolated quantum wells have been studied, and the thermal activation energies associated with the effective barriers for electrons and holes have been determined. In CdTe/ZnTe heterostructures, the binding energies of an exciton with a heavy hole have been determined as functions of the quantum well width. The multiphonon Raman spectra that exhibit distinctive features, such as the weak intensity of nLO phonon lines of ZnTe (n < 8), the absence of their dependence on the number n (n > 2), and the multiple participation in scattering of acoustic LA phonons with large wave vector, have been investigated. The results have been explained based on the concept of the relaxation of hot excitons over the exciton band. 相似文献
8.
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
9.
Laser excited hot electrons in GaAs relax by LO phonon emission within a few hundred femtoseconds, leading to a series of peaks in the distribution of hot electrons in the conduction band, which we observe in luminescence. We find that the luminescence peaks shift according to the acceptor binding energy for C?, Ge?, Zn?, and Be-p-doped GaAs layers grown by MBE and LPE. Thus we prove that recombination is between hot electrons and neutral acceptors. The series of peaks due to electrons from the heavy hole band agree well with band structure, while peaks due to those from light holes are about 15 meV lower than expected from the band structure. We show that the discrepancy is not due to heating or surface fields. The peak separation in the luminescence ladder is about 6% larger than the LO energy suggesting emission of renormalised LO phonons. We find thermalisation by LO emission also in GaAs nipi doping superlattices. In nipi crystals the emission is shifted to higher energies (by 12 meV for light and by 6 meV for heavy holes) due to a change in band structure caused by the space charge fields. 相似文献
10.
R. Ebert H. Pascher G. Appold H. G. Häfele 《Applied Physics A: Materials Science & Processing》1977,14(2):155-159
We report for the first time stimulated magneto-Raman scattering inp-type InSb. Two different Raman scattering processes were observed. The first one has a Raman shift of about 2cm−1/kG and is observed at magnetic fields up to 30kG. The other one is observable only at high magnetic fields above 30kG and
shows Raman shifts between 1.2cm−1 and 3.0cm−1 with a tuning rate of about 0.2cm−1/kG. The first process can be interpreted either as spin-flip Raman scattering by photo-excited electrons in the conduction
band or as Raman scattering by holes in the valence band involving transitions from heavy to light hole states. The other
Raman shift observed seems to occur on account of transitions between the heavy hole ladders. 相似文献
11.
V. I. Belyavskii 《Russian Physics Journal》1982,25(3):282-286
An expression is obtained for the secondary radiation section of polar semiconductors due to radiation trapping of electrons or holes at deep impurity levels with the participation of intermediate quasilocal states. The dependence of the section on the frequency of the exciting monochromatic wave is determined mainly by the nonequilibrium electron distribution function, which is a number of equidistant peaks. The spacing between adjacent peaks equals the frequency of the longitudinal optical (LO) phonon, while the peak width is determined by the dispersion of the LO phonons. The distinction between the radiation and Lorentz line shapes is also associated with the form of the electron distribution function.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 89–93, March, 1982. 相似文献
12.
The phonon thermal conductivity values in Zn-doped GaSb are explained for hole concentrations ranging from 2 × 1017 to 4 × 1019 cm-3. The concentration dependence of thermal conductivity above 3 × 1018 cm-3 is similar to other doped materials and is explained by considering the scattering of phonons by free electrons (holes) given by Ziman and Kosarev and applying the screening effects suggested by Crossby and Grenier. The density-of-states effective mass is kept constant and the dilatation deformation potential is found to increase with hole concentration. For impurity concentrations less than 3 × 1018 cm-3, the thermal conductivity is found to increase with hole concentration. Since this concentration region is below the metal-insulator transition, the theory of scattering of phonons by holes bound to the impurity atoms explains the conductivity results. The values of acceptor hole radius and deformation potential constants are in agreement with the experimental values. 相似文献
13.
The theoretical analysis for the Raman scattering by 2LO phonons is carried out. The scattering process is considered, taking into account the Wannier excitons and the free electron-hole pairs as intermediate states. 相似文献
14.
The lifetimes of quantum excitations are directly related to the electron and phonon energy linewidths of a particular scattering
event. Using the versatile double time thermodynamic Green’s function approach based on many-body theory, an ab-initio formulation of relaxation times of various contributing processes has been investigated with newer understanding in terms
of the linewidths of electrons and phonons. The energy linewidth is found to be an extremely sensitive quantity in the transport
phenomena of crystalline solids as a collection of large number of scattering processes, namely, boundary scattering, impurity
scattering, multiphonon scattering, interference scattering, electron–phonon processes and resonance scattering. The lattice
thermal conductivities of three samples of GaAs have been analysed on the basis of modified Callaway model and a fairly good
agreement between theory and experimental observations has been reported. 相似文献
15.
The complex zeroes of dielectric response function of a doped GaAs superlattice are computed to study the frequencies and
damping rates of oscillations in coupled electron-hole plasma. The real part of a complex zero describes the plasma frequency,
whereas imaginary part of it yields the damping rate. Strong scattering of charge carriers from random impurity potentials
in a doped GaAs superlattice gives rise to a large value of damping rate which causes over-damping of plasma oscillations
of coupled electron-hole gas below qc, a critical value of wave vector component (q) along the plane of a layer of electrons (holes). The plasma oscillations which correspond to electrons gas enter into over-damped
regime for the case of weak coupling between layers. Whereas, plasma oscillations which belong to hole gas go to over-damped
regime of oscillations for both strong as well as weak coupling between layers. The damping rate shows strongq-dependence forq < qc, whereas it weakly depends onq forq ≥q
c
. The damping rate exhibits a sudden change atq =q
c
, indicating a transition from non-diffusive regime (where collective excitation can be excited) to diffusive regime (over-damped
oscillations). 相似文献
16.
A. Bostwick T. Ohta J. L. McChesney T. Seyller K. Horn E. Rotenberg 《The European physical journal. Special topics》2007,148(1):5-13
We have determined the electronic bandstructure of clean and potassium-doped single layer graphene, and fitted the
graphene π
bands to a one- and three-near-neighbor tight binding model. We characterized the quasiparticle dynamics using angle resolved
photoemission spectroscopy. The dynamics reflect the interaction between holes and collective excitations, namely plasmons,
phonons, and electron-hole pairs. Taking the topology of the bands around the Dirac energy for n-doped graphene into account,
we compute the contribution to
the scattering lifetimes due to electron-plasmon and electron phonon coupling. 相似文献
17.
Monte Carlo method is employed for the calculations of electron and hole transport characteristics of cubic and hexagonal
GaN at T = 300 K in the fields of E ≤ 1000 kV/cm−1. It is shown that electron drift velocity and mobility is heavily reduced in hexagonal crystals due to additional phonon
modes (~ 26 meV) and by fast electron scattering between the lowest Γ1 valley and the minimally (~ 400 meV) up-shifted Γ3 valley. Intervalley scattering is mediated most efficiently by the low-energy (~ 2 meV) acoustic phonons. The randomizing
scattering is even more pronounced in p-type crystals where the sub-bands of light and heavy holes merge at the Γ-point of Brillouin zone. Cubic phase crystals are
concluded to be advantageous for ultrafast electronic and photonics device performance because electron drift mobility is
higher by an order of magnitude, and the hole mobility is several times higher than those in hexagonal phase. 相似文献
18.
A. Lushchik M. Kirm I. Kudryavtseva C. H. Lushchik I. Martinson V. Nagirnyi 《辐射效应与固体损伤》2013,168(6-12):537-543
The processes of multiplication of electronic excitations (MEE), connected with the creation of secondary excitons or electron-hole (e-h) pairs by hot conduction electrons, are realized in wide-gap metal halides and oxides. In oxides, secondary e-h pairs can be also formed by 27-40 v eV photons due to L 1 VV Auger transitions (with the participation of 2s oxygen holes). The excitation spectra of luminescence and the creation spectra of electron F centres or hole V centres have been measured for Na 6 Al 6 Si 6 O 24 (NaI) 2x sodalites and MgO:Be, respectively, at 8-80 v K. A high local density of excitations has been revealed under MEE conditions in KBr and Br sodalites with self-trapping excitons and holes. 相似文献
19.
A. B. Talochkin S. P. Suprun A. V. Efanov I. G. Kozhemyako V. N. Shumskii 《JETP Letters》2001,73(6):297-300
Raman scattering by optical phonons in unstrained Ge quantum dots obtained in GaAs/ZnSe/Ge/ZnSe structures was studied using molecular beam epitaxy. A shift in the E 1, E 1+Δ1 resonance energy due to the quantization of the spectrum of electron and hole states in quantum dots was observed. The properties observed were explained with the use of a simplest model of localization with allowance for the spectrum of Ge electron states. 相似文献
20.
It is predicted that resonance coupling between two discrete electron energy levels corresponding to different size-quantization
quantum numbers and different Landau quantum numbers can occur in a quantum well in a quantizing magnetic field. The resonance
coupling is due to the interaction of an electron with LO phonons and results in the formation of polaron states of a new type. It is shown that for a certain value of the magnetic
field, which depends on the splitting of the electron size-quantization levels, the absorption peak and the two-phonon resonance
Raman scattering peak split into two components, the separation between which is determined by the electron-phonon coupling
constant. The resonance coupling between size-quantization levels with the same Landau quantum numbers is also studied. The
splitting of the peaks in this case is virtually independent of the magnetic field and can be observed in much weaker fields.
The experimental observation of the effect will make it possible to determine the relative position of the electronic levels
and the electron-phonon coupling constant.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 7, 511–515 (10 April 1997) 相似文献