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1.
加偏置电场的抛物量子阱中的电光效应 总被引:2,自引:2,他引:0
本文利用密度矩阵方法得到了加偏置电场的抛物量子阱中电光效应的解析表达式,并以典型的GaAs抛物量子阱为例进行了数值计算研究结果表明,电光效应随偏置电场和抛物势频率的增大而增强,同时也表明GaAs量子阱中的电光效应比体GaAs中的要强一个数量级以上。 相似文献
2.
The absorption constant for intraband transitions in parabolic multiquantum well structures is calculated and compared with intraband absorption in a square well superlattice. The parabolic multiple quantum well structure may be used as an Infrared detector with the possibility of lower leakage current compared to one made of square wells. 相似文献
3.
《Solid State Communications》1987,61(10):601-605
We report the observation of electronic light scattering in photoexcited parabolic GaAsAlxGa1-xAs quantum wells. The spectra show sharp peaks corresponding to transitions between sublevels in the conduction band. The precision of the measurements allows a test of the simple harmonic oscillator model for the energy level structure. The energy gap and alloy composition of the AlxGa1-xAs layers are determined from resonance Raman scattering by optical phonons. We use these results to calculate the conduction band offset Qe. We obtain Qe ∼ 0.7, in agreement with recent experiments in square quantum wells. 相似文献
4.
Summary We study the subband energies in quantum wells and quantum wires in the presence of a parallel magnetic field in non-parabolic
semiconductors, on the basis of a generalized dispersion relation considering all types of anisotropies of the energy-band
parameters within the framework ofk·p formalism, by formulating the respective electron energy spectra. It is found, by takingn-Cd3As2 as an example, that the subband energies are greater for quantum wires and smaller for quantum wells, respectively. The magnetic
field diminishes the above values and the corresponding well-known results for quantum-confined parabolic semiconductors have
also been obtained from our generalized expressions under certain limiting conditions. 相似文献
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7.
Ultrastrong coupling is studied in a modulation-doped parabolic potential well coupled to an inductance-capacitance resonant circuit. In this system, in accordance to Kohn's theorem, strong reduction of the energy level separation caused by the electron-electron interaction compensates the depolarization shift. As a result, a very large ratio of 27% of the Rabi frequency to the center resonance frequency as well as a polariton gap of width 2π × 670 GHz are observed, suggesting parabolic quantum wells as the system of choice in order to explore the ultrastrong coupling regime. 相似文献
8.
《Superlattices and Microstructures》1993,13(4):459
Hot electron cooling in variously structured and doped quantum wells and superlattices has been studied by low temperature steady-state photoluminescence. A parabolic quantum well realized by thickness grading of Al0.3Ga0.7As and GaAs epitaxial layers deposited by molecular beam epitaxy with electron level spacings of ∼25 meV did not show increased electron plasma temperatures compared to thick epitaxially deposited GaAs or square quantum wells with electron level spacings greater than the LO phonon energy of GaAs; this implies that mechanisms involving intersubband Δk ≠ 0 transitions and interfacial recombination are dominant in the parabolic structure. Investigations as a function of carrier concentration in modulation-doped quantum wells and n-type superlattices with strong miniband formation indicate that increasing the carrier concentration in either structure above ∼ 5 × 1017 cm-3 significantly increases the electron plasma temperatures, even under low light excitation, suggesting that such structures may be suited for high efficiency hot electron photovoltaic and photoelectrochemical cells. 相似文献
9.
This paper attempts to summarize some of the salient properties of excitons in GaAs quantum wells and in doing so it will emphasize work at AT&T Bell Labs with which the authors have been associated. Although the text relies heavily on published material, an effort has been made to stress new material, and where feasible, unpublished aspects, e.g., figures, related to earlier work. Topics discussed on the quasi-2D excitons in GaAs quantum well include: their inherent tendency for intrinsic free-exciton emission, exciton binding energies, bound and localized excitons including biexcitons and excitons bound to neutral impurities, effects of n- and p-type modulation and antimodulation doping, and the developments leading to a proposed set of quantum well parameters that results in acceptable fits to the observed exciton transitions for GaAs quantum wells with both square and parabolic potential profiles. 相似文献
10.
C. J. G. M. Langerak B. N. Murdin C. M. Ciesla J. Oswald A. Homer G. Springholz G. Bauer R. A. Stradling M. Kamal-Saadi E. Gornik C. R. Pidgeon 《Physica E: Low-dimensional Systems and Nanostructures》1998,2(1-4)
Landau-level lifetimes are determined from saturation cyclotron resonance (CR) in wide parabolic wells, quantum wells and bulk PbTe–Pb1−xEuxTe systems. These narrow gap structures exhibit strong band non-parabolicity necessary to terminate the normally equi-spaced Landau-level ladder. It was not possible to saturate the bulk sample, but short lifetimes, of between 1.5 and 8 ps, were obtained for the wide parabolic well and the quantum well, respectively, utilising a multi-level rate equation model. We also report the first pump–probe cyclotron resonance result in an InAs–AlSb quantum structure. The pump–probe experiment provides a direct determination of the lifetime, giving τ=40 ps in this InAs–AlSb sample. This shows good agreement with an 8×8k·p calculation. 相似文献
11.
Z. P. Wang X. X. Liang X. Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(1):41-46
Polaron effects on excitons in parabolic quantum wells are
studied theoretically by using a variational approach with the so-called
fractional dimension model. The numerical results for the exciton binding
energies and longitudinal-optical phonon contributions in
GaAs/Al0.3Ga0.7As parabolic quantum well structures are obtained as functions of the well width. It is shown that the exciton binding energies
are obviously reduced by the electron (hole)-phonon interaction and the polaron effects are un-negligible. The results demonstrate
that the fractional-dimension variational theory is effectual in the investigations of excitonic polaron problems in parabolic
quantum wells. 相似文献
12.
The energy of a biexciton in a GaAs/AlxGa1?xAs quantum well structure with finite barriers is investigated by using the geometrical model of two-dimensional biexcitons proposed by Singh et al. [J. Singh, D. Birkedal, V.G. Layssenko, J.M. Hvam, Phys. Rev. B 53 (1996) 15909; I.-K. Oh, J. Singh, Phys. Rev. B 60 (1999) 2528]. A fractional-dimensional approach is used to obtain the binding energy of the biexciton in both square quantum wells and parabolic quantum wells. Theoretical results show that the binding energy of a biexciton in a finite quantum well exhibits a maximum with increasing well width. The ratio of the binding energy of a biexciton to that of an exciton in a quantum well structure is found to be sensitive to the electron-to-hole mass ratio and larger than that in the three-dimensional system. The results agree fairly well with previous experimental results. The results of our approach are also compared with those of earlier theories. 相似文献
13.
Intra-subband transitions caused by light absorption in a parabolic quantum well is considered taking into account the scattering by ionized impurity centers. To calculate the scattering matrix element, the Born approximation is used and the interaction with the impurity is described by the Coulomb potential. An analytical expression for the absorption coefficient of processes with the initial absorption of photon and further scattering by an ionized impurity center is obtained. For absorption coefficient the frequency characteristics and dependence on the width of quantum well are examined. 相似文献
14.
The energy levels and binding energies of a hydrogenic impurity in GaAs spherical quantum dots with radius R are calculated by the finite difference method. The system is assumed to have an infinite confining potential well with radius R, which can be viewed as a hard wall boundary condition. The parabolicity of the conduction band profile for GaAs material can be viewed as a parabolic potential well. The energy levels and binding energies are depended dramatically on the radius of the quantum dot and the parabolic potential well. The results show that parabolic potential can remarkably alter the energy level ordering and binding energy level ordering of hydrogenic impurity states for the quantum dot with a smaller radius R. 相似文献
15.
The intersubband optical absorption in symmetric and asymmetric, single and coupled, double GaAs/ Ga1 − xAlxAs quantum wells is calculated. The results have been obtained in the presence of a uniform electric field as a function of the potential symmetry, size of the quantum well, and coupling parameter of the wells. In coupled double quantum wells we obtain a large Stark effect that can be used to fabricate tuneable photodetectors. We show that the effect of an applied electric field on the intersubband optical absorption is similar to changes in the dimensions of the structure. This behaviour in the intersubband optical absorption for different wells and barrier geometries can be used to study these systems in regions of interest, without the need for the growth of many different samples. 相似文献
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《Superlattices and Microstructures》1995,17(2):187-191
The exciton wavefunction in parabolic quantum wells is calculated using variational techniques and effective mass theory. The influences of the potential shape and of confinement on the exciton binding energies are studied. The results are in good agreement with previous calculations. The oscillator-strength of excitons in GaAs/Ga1-xAlxAS quantum wells has a maximum value very close to the cross-over from three to two dimensions. 相似文献
18.
S. Baskoutas C. Garoufalis A. F. Terzis 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,84(2):241-247
In the present theoretical study, the linear and third-order nonlinear optical absorption coefficients have been calculated
in GaAs/Ga1−x
Al
x
As inverse parabolic quantum wells (single and double) subjected to an external electric field. Our calculations are based
on the potential morphing method in the effective mass approximation. The systematic theoretical investigation contains results
with all possible combinations of the involved parameters, as quantum well width, quantum barrier width, Al concentration
at each well center and magnitude of the external electric field. Our results indicate that in most cases investigated, the
increase of the electric field blue-shifts the peak positions of the total absorption coefficient. In all cases studied it
became apparent that the incident optical intensity considerably affects the total absorption coefficient. 相似文献
19.
We studied the influence of the nuclear spin diffusion on the dynamical nuclear polarization of low dimensional nanostructures subject to optical pumping. Our analysis shows that the induced nuclear spin polarization in semiconductor nanostructures will develop both a time and position dependence due to a nonuniform hyperfine interaction as a result of the geometrical confinement provided by the system. In particular, for the case of semiconductor quantum wells, nuclear spin diffusion is responsible for a nonzero nuclear spin polarization in the quantum well barriers. As an example we considered a 57 Å GaAs square quantum well and a 1000 Å Al x Ga1?x As parabolic quantum well both within 500 Å Al0.4Ga0.6As barriers. We found that the average nuclear spin polarization in the quantum well barriers depends on the strength of the geometrical confinement provided by the structure and is characterized by a saturation time of the order of few hundred seconds. Depending on the value of the nuclear spin diffusion constant, the average nuclear spin polarization in the quantum well barriers can get as high as 70% for the square quantum well and 40% for the parabolic quantum well. These results should be relevant for both time resolved Faraday rotation and optical nuclear magnetic resonance experimental techniques. 相似文献