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1.
The electron drift mobility in Γ conduction band of GaAs has been calculated before, but for the first time, we have made
attempts to estimate the electron mobilities in higher energy L and X minima. We have also calculated the value of mobility
of two-dimensional electron gas needed to predict hetero-structure device characteristics using GaAs. Best scattering parameters
have been derived by close comparison between experimental and theoretical mobilities. Room temperature electron mobilities
in Γ, L and X valleys are found to be nearly 9094, 945 and 247 cm2/V-s respectively. For the above valleys, the electron masses, deformation potentials and polar phonon temperatures have been
determined to be (0.067, 0.22, 0.39m
0), (8.5, 9.5, 6.5 eV), and (416, 382, 542 K) as best values, respectively. The 2-DEG electron mobility in Γ minimum increases
to 1.54 × 106 from 1.59 × 105 cm2/V-s (for impurity concentration of 1014 cm−3) at 10 K. Similarly, the 2-DEG electron mobility values in L and X minima are estimated to be 2.28 × 105 and 1.44 × 105 cm2/V-s at 10 K, which are about ∼4.5 and ∼3.9 times higher than normal value with impurity scattering present.
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2.
Conclusions The studies performed here have shown that the superlattice samples studied exhibit photoluminescence spectra which agree
with the Kronig-Penney model, although in calculating the energies of the radiative transitions it is necessary to take into
account the binding energy of the excitons,E
B. Due to the exciton—phonon interaction, the 1HH peak breaks up on the long wavelength side into a Poisson distribution. The
energy of the LO phonon so determined is 34 meV. Bands due toD
0-A
0 andD
0X transitions, caused by remaining low-level impurities in the GaAs crystals are also observed.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 61, Nos. 3–4, pp. 241–245, September–October, 1994. 相似文献
3.
I. K. Polushina Yu. V. Rud’ T. N. Ushakova V. Yu. Rud’ 《Physics of the Solid State》1999,41(7):1084-1087
The first results obtained in studies of the temperature dependences of electrical conductivity and Hall constant of n-CdGeAs2 single crystals prepared by low-temperature crystallization are reported. It has been established that the method developed
permits growing single crystals with a free-electron concentration ⋍(1−2)×1018 cm−3 and a Hall mobility ⋍10000 cm2/(Vs) at T=300 K. It is shown that the temperature dependence of Hall mobility exhibits a behavior characteristic of electron scattering
by lattice vibrations, whereas below 150 K a deviation from this law is observed to occur evidencing an increasing contribution
of static lattice defects to scattering. The Hall mobility in the crystals prepared was found to reach ⋍36000 cm2/(Vs) at 77 K. Photosensitive heterojunctions based on n-CdGeAs2 single crystals were prepared. The spectral response of the photosensitivity of these structures is analyzed. It is concluded
that this method is promising for preparation of perfect CdGeAs2 crystals.
Fiz. Tverd. Tela (St. Petersburg) 41, 1190–1193 (July 1999) 相似文献
4.
The effect of smooth interface potential on the electron tunneling in the GaAs/AlAs(111) structures with thin layers is studied using the pseudopotential method. The transition region between the structure components
is represented by a half-period of the hexagonal (GaAs)
3(AlAs)3
(111) superlattice. It is shown that the allowance for the smooth potential results in a decrease in the Γ-L-mixing, Fano-resonance
narrowing, and disappearance of interface states at the GaAs/AlAs(111) interface as compared to the abrupt-interface model. The shifts of the lowest Γ-and L-resonances observed for the structures
with the layer thickness <2 nm amount to ∼0.1 eV, which is in good agreement with the behavior of levels in quantum wells.
The transmission coefficient of electrons with the energies 0–0.5 eV above the GaAs conduction-band bottom obtained by multivalley calculation is close to that calculated with allowance for the lowest conduction
band states Γ
1
(1)
and Γ
1
(2)
of superlattice and Γ
1 and L
1 of binary crystals. This indicates that a two-valley superlattice model of the smooth GaAs/AlAs(111) interface can be developed.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 7–13, July, 2007. 相似文献
5.
Completely self-consistent ab initio calculations of scattering of electrons between the lowest minima of the conduction band by short-wavelength phonons are
performed for the first time for a group of А
III
В
V semiconductor crystals. The structure constants, electron and vibrational spectra, and probabilities of scattering are calculated
for the crystals from unified positions within the electronic density functional method. The theory does not involve any phenomenological
assumptions on positions of minima in the conduction band, effective carrier masses, interatomic forces, or scattering probabilities.
The electron-phonon coupling constants (the deformation potentials) for actual Γ−X, Γ−L, and X−L transitions for scattering between the nonequivalent X−X and L−L valleys in the conduction bands of AlP, AlAs, AlSb, GaP, GaAs, GaSb, InP, InAs, and InSb crystals with sphalerite structure
are calculated. Results obtained are compared with theoretical calculations within the phenomenological rigid ion model and
with those performed by the selfconsistent frozen phonon method. 相似文献
6.
The energy spectra of traps in NaCl crystals have been studied in detail by the method of thermoluminescence. Crystals of
NaCl were undoped but treated thermally in different ways. The activation energies of traps form a single oscillator series,
E
n
=ℏω
TL
(n+1/2), ℏω
TL
=903 cm-1. Contrary to other previously studied crystals with complex lattices, the corresponding line ℏω
Ram
=ℏω
TL
was not found in Raman spectra of NaCl. It is assumed that the oscillator rule is governed by the polaron nature of traps.
The trap activation energy is determined by the vibration level from which the transition of the charge carrier to the excited
luminescence centre is made possible and depends on the distance between these centres. 相似文献
7.
Experimental Coulomb isotope shifts δE
Coul from K
α transitions, and radius differences δ〈r
2〉
eμ measured by electron scattering and muonic atom X-rays were used to derive ‘experimental’ coefficients C
1,exp for 54 isotope pairs of 18 elements from Mo to U. A χ2-analysis shows that these experimental coefficients are – on average – 3.5% lower than the theoretical C
1 values calculated by Seltzer, or more precisely: C
1,exp=0.965(± 0.014)×C
1. The need for more accurate theoretical calculations is stressed, and consequences of this deviation are discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
Alexander G. Andreev Stefka G. Tsintsarska Maria Dimitrova-Ivanovich Ivaylo Polyanski Mladen Georgiev Alexander D. Gochev 《Central European Journal of Physics》2004,2(2):329-356
The temperatureT dependencies ρ(T) of normal state electric resistivitiesρ
c
(axial) andρ
ab
(in plane) of single-layer high-T
c
superconductors show common trends: AsT is raised, the resistivity first drops steeply before it starts rising αT above an apparent semiconductor-to-metal crossoverT
cross
. To analyze ρ(T) we plottT/ρ againstT at various dopingsx for bothρ
c
andρ
ab
.T/ρ is inversely proportional to the traversal time across a potential barrier as an ionic particle drifts in an electric field.
We findT/ρ in good agreement with theT dependence of the quantum rate of migrating particles: AsT is raised, a zero-point rate at the lowestT is extended to a nearly flat plateau before a thermally activated branch sets in. We also find evidence for the admixture
of 1- & 2-phonon absorptions below the Arrhenius range. These features shape the semiconductor-like branch below T
cross
. AboveT
cross
a metallic-like branch sets in, its αT character deriving from the field coupling of the migrating particle. Our analysis suggests that metal physics may not suffice
if ionic features play a role in transport. We attribute our conclusions to the drift of strong-coupling polarons along Cu−O
bonds. These “bond polarons” originate from carrier scattering by double-well potentials associated with the bonds. A bond
polaron dissociates to a free hole as it passes onto a neighboring O-O link. 相似文献
9.
BES II data for J/Ψ↦K
*(890)Kπ reveal a strong κ peak in the Kπ S-wave near threshold. Both magnitude and phase are determined in slices of Kπ mass by interferences with strong K
0(1430), K
1(1270) and K
1(1400) signals. The phase variation with mass agrees within errors with LASS data for Kπ elastic scattering. A combined fit is presented to both BES and LASS data. The fit uses a Breit-Wigner amplitude with an
s-dependent width containing an Adler zero. The κ pole is at (760±20(stat)±40(syst)) - i(420±45(stat)±60(syst)) MeV. The S-wave I = 0 scattering length a
0 = 0.23±0.04 m
π
-1 is close to the prediction 0.19±0.02 m
π
-1 of Chiral Perturbation Theory at O(p
4).
An erratum to this article can be found at . 相似文献
10.
Starting from an analytical macroscopic/phenomenological model yielding the self-bias voltage as a function of the absorbed
radio-frequency (rf) power of an asymmetric capacitively coupled discharge in NF3 this paper studies the dependence of the ion flux onto the powered electrode on the gas pressure. An essential feature of
the model is the assumption that the ions' drift velocity in the sheath near the powered electrode is proportional to E
α, where E=−ΔU (U being the self-bias potential), and α is a coefficient depending on the gas pressure and cross section of elastic ion-neutral
collisions. The model also considers the role of γ-electrons, stochastic heating as well as the contribution of the active
electron current to the global discharge power balance. Numerically solving the model's basic equations one can extract the
magnitude of the ion flux (at three different gas pressures) in a technological etching device (Alcatel GIR 220) by using
easily measurable quantities, notably the self-bias voltage and absorbed rf power. 相似文献
11.
S. Narita M. Egawa K. Suizu M. Katayama S. Mizukami 《Applied Physics A: Materials Science & Processing》1973,2(3):151-156
The hydrostatic pressure effects on CdxHg1−xTe alloys have been investigated. In the relatively low pressure region, we find an anomaly in each Hall coefficient vs. pressure
curve for the alloys (x<0.09), which is attributed to the inversion of the Γ8/Γ6 energy bands. In the relatively high pressure region, the electrical resistivities of the alloy crystals (x>0.09) show changes of three stages with increase of pressure. The crystal structures corresponding to the three stages are
studied by an X-ray diffraction analysis. It is found that the crystal structure of the alloys exhibits transitions from the
zinc-blende to the rock salt type and at last to the hexagonal cinnabar type. 相似文献
12.
Intervalley electron scattering by phonons in (AlAs)1(GaAs)3(001) superlattices is studied using the pseudopotential method and a phenomenological model of the bonding forces. The deformation
potentials between the conduction band extrema of the superlattice involving short-and long-wavelength phonons are calculated.
It is shown that the mixing of states from the zinc-blende L valleys plays a greater role in intervalley scattering in a superlattice than the Γ-X mixing. In particular, due to L-L mixing, the Γ-X
3 transitions, analogous to Γ-L transitions in zinc blende, have higher intensities than the analogues of Γ-X transitions (Γ1-M
5 and (Γ1-Γ3 transitions). The deformation potentials averaged over the scattering channels in the superlattice agree with the corresponding
potentials in a solid solution, but all transitions in the superlattice have higher intensities for the lower states. 相似文献
13.
Yu. F. Markov E. M. Roginskii A. S. Yurkov 《Journal of Experimental and Theoretical Physics》2012,114(2):288-295
Information is obtained about the temperature behavior of the order parameter of a phase transition by theoretical and experimental
investigation of odd (acoustic and IR-active) phonons that appear in the Raman scattering spectra from the X points of the Brillouin zone (BZ) boundary in the paraphase of Hg2Cl2 crystals and are induced by the phase transition, unit-cell doubling, and the X → Γ folding in the BZ. The relevant critical exponents are determined, whose values are in agreement with the results of
X-ray diffraction measurements and, within the Landau phenomenological theory of phase transitions, indicate that the phase
transition in these crystals is close to the tricritical point. 相似文献
14.
We have investigated the superconducting properties of the Bi1.7 Pb0.3Sr2Ca2−xCe
x
Cu3O10+δ system with x=0.00, 0.02, 0.04, 0.08 and 0.1 by X-ray diffraction and magnetic susceptibility. The substitution of Ce for Ca has been found
to drastically change the superconducting properties of the system. X-ray diffraction studies on these compounds indicate
decrease in the c-parameter with increased substitution of Ce at Ca site and volume fraction of high T
c (2 : 2 : 2 : 3) phase decreases and low T
c phase increases. The magnetic susceptibility of this compound shows that the diamagnetic on set superconducting transition
temperature (onset) varies from 109 K to 51 K for x=0.00, 0.02, 0.04, 0.08 and 0.1. These results suggest the possible existence of Ce in a tetravalent state rather than a trivalent
state in this system; that is, Ca2+ → Ce4+ replacement changes the hole carrier concentration. Hole filling is the cause of lowering T
c of the system. 相似文献
15.
Nguyen Thi Minh Hien Kiok Han Xiang‐Bai Chen Jung Chul Sur In‐Sang Yang 《Journal of Raman spectroscopy : JRS》2012,43(12):2020-2024
We present the results of polarized Raman spectroscopy of hexagonal BaFe12O19 single crystal. The spectra, recorded from 200 to 800 cm–1 and 1100 to 1700 cm–1 in the 20–250 K temperature range, are analyzed on the basis of both crystal vibrations and spin‐waves. In the low wavenumber range, the Γ‐point phonons are observed. In the high wavenumber range, phonon mixings are observed; more interestingly, four modes of spin‐waves are identified in hexagonal BaFe12O19. Both have not been studied previously. Our analyses of the spin‐waves provide an optical method for quantitatively estimating the spin exchange interactions in hexagonal BaFe12O19. The four strong exchange integrals are found to have the values of Jce = 1.31 meV, Jae = 1.36 meV, Jcd = 1.46 meV, and Jbd = 1.71 meV. Our results also indicate that at ~200 and ~80 K, there would be additional spin‐ordering transitions in hexagonal BaFe12O19. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
16.
The dependence of the intrinsic line width Γ of electron and hole states due to inelastic scattering on the wave vector k
∥ in the occupied surface state and the first image potential state on the Cu(111) and Ag(111) surfaces has been calculated
using the GW approximation, which simulates the self-energy of the quasiparticles by the product of the Greens’s function
and the dynamically screened Coulomb potential. Different contributions to the relaxation of electron and hole excitations
have been analyzed. It has been demonstrated that, for both surfaces, the main channel of relaxation of holes in the occupied
surface states is intraband scattering and that, for electrons in the image potential states, the interband transitions play
a decisive role. A sharp decrease in the intrinsic line width of the hole state with an increase in k
∥ is caused by a decrease in the number of final states, whereas an increase in Γ of the image potential state is predominantly
determined by an increase of its overlap with bulk states. 相似文献
17.
N. N. Loshkareva Yu. P. Sukhorukov B. A. Gizhevskii S. V. Naumov A. A. Samokhvalov A. S. Moskvin T. A. Belykh 《Physics of the Solid State》1998,40(3):383-388
Irradiation of various single-crystal CuO faces [ac,bc,(110)] with 4.6-MeV He+ ions has been found to result in reduction of CuO to Cu2O and Cu on the irradiated and unirradiated sides, lifting of forbiddenness from optical transitions in the [CuO4]7− electron center in the 0.7–0.95-eV energy range, a change in dichroism near the bands corresponding to transitions in the
hole centers, [CuO4]5−, and electron centers, [CuO4]7−, as well as in a resonant increase of absorption at 0.95–1.30 eV with an unusual polarization dependence. The results of
He+ irradiation of CuO single crystals are discussed in terms of a model of the nucleation of the phase of polar (electron and
hole) centers in copper-oxygen systems.
Fiz. Tverd. Tela (St. Petersburg) 40, 419–424 (March 1998) 相似文献
18.
We report the development of a method for recording the low-temperature (T=6 K) near-IR inelastic light scattering spectra and the observation of electronic scattering on the transitions 1s
3/2(Γ8) → 2s
3/2(Γ8) between the ground and excited states of different shallow acceptor centers in a n-type semi-insulating crystal si-GaAs (n=1.0 × 108 cm−3) and in a doped p-InP crystal (p=3.6×1017 cm−3). Moreover, a new line, associated with the transition 1s
3/2(Γ 8) → 2p
3/2(Γ8) and due to a dielectric local mode, recorded for the first time in the spectra of narrow-gap semiconductors, was found in
the residual-frequency band in the p-InP spectrum between TO(Γ) and LO (Γ) phonons.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 5, 334–339 (10 March 1998) 相似文献
19.
F. Vanderbist P. Leleux C. Angulo E. Casarejos M. Couder M. Loiselet G. Ryckewaert P. Descouvemont M. Aliotta T. Davinson Z. Liu P. J. Woods 《The European Physical Journal A - Hadrons and Nuclei》2006,27(2):183-186
The 15O(α,α)15O elastic scattering is investigated using a 15O radioactive beam and a He gas cell limited by Mylar windows. The width of a 19Ne state at an excitation energy of 5.35MeV is measured as Γα = 3.2±1.6keV, in agreement with charge symmetry estimate. 相似文献
20.
Ting LUO Yi ZHANG Xing-guo LI Li LIN Yue-yang ZHANG Qing-rong FENG 《Frontiers of Physics in China》2008,3(1):55-60
Systematic studies of synthesizing behaviors of sol-gel YBa2Cu3O7−x
samples in flowing oxygen atmosphere and their superconductivity have been performed. A set of high temperature ρ-T curves has been obtained for the whole synthesizing process. After four rounds of synthesizing, the resistivity of the sample
was around ρ=1.00×10−3Ω · cm at room temperature. The ρ-T curve of the fourth round shows that the orthorhombic to tetragonal phase transformation of the sample occurs around 600
°C, which is lower than that of the YBa2Cu3O7−x
sample prepared by conventional solid-state reaction method. Other measurements, such as X-ray diffraction, SEM measurement
and low temperature R-T and M-T measurement, were also performed. And the R-T and M-T measurement results suggest that during the synthesizing process, there exist some state at which the sample has better superconductivity
than the other states. Moreover, we found screw dislocations presenting on the sample broken surface from the SEM images.
This will change the concept that the screw dislocations can only grow on the surface of the YBCO thin films and single crystals.
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