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1.
Tight-binding calculations of the subband structures of zincblende-semiconductor [001] quantum wells
The scattering-theoretic T-matrix method is used to calculate the subband structures of GaAs?ZnSe and ZnSe?ZnSxSe1?x [001] quantum wells within an empirical tight-binding model, that includes the bulk Г6, Г7 and Г8 valence- and conduction bands. The resulting confinement energies for vanishing lateral crystal momentumk ‖ are compared with those, that are obtained from a simple effective mass model and effects are found and predicted which the effective mass model cannot account for. The effect of the band nonparabolicity and the influence of the microscopic sequence of atomic layers, which determines the symmetry properties of a quantum well, are studied for the GaAs?ZnSe wells. 相似文献
2.
V. K. Kononenko I. S. Manak S. V. Nalivko V. A. Shevtsov D. S. Shulyaev 《Journal of Applied Spectroscopy》1997,64(2):234-241
Laser diodes and amplifiers of a new type based on asymmetric quantum-well heterostructures having a set of effective layers
of different thickness are considered. In distinction to conventional laser heterostructures, for such modified quantum-well
systems the gain spectrum and the set of lasing frequencies can be varied over a wide range by choosing the widths and the
component composition of quantum wells and barrier regions. The transformation of the amplification bands for the TE and TM
modes with the excitation current was studied. Calculations were performed for the GaAs−AlxGa1−xAs system. In a model of direct transitions the subbands of heavy and light holes as well as changes in the polarization factor
with the frequency of light are considered. A number of questions associated with spectral broadening of lines and determination
of radiation localization and distribution of quasi-Fermi levels in the effective layers are discussed.
B. I. Stepanov Institute of Physics, Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Belarusian
State University. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 221–227, March–April, 1997. 相似文献
3.
L. V. Butov A. V. Mintsev A. I. Filin K. Eberl 《Journal of Experimental and Theoretical Physics》1999,88(5):1036-1044
The kinetics of indirect photoluminescence of GaAs/AlxGa1−x
As double quantum wells, characterized by a random potential with a large amplitude (the linewidth of the indirect photoluminescence
is comparable to the binding energy of an indirect exciton) in magnetic fields B≤12 T at low temperatures T≥1.3 K is investigated. It is found that the indirect-recombination time increases with the magnetic field and decreases with
increasing temperature. It is shown that the kinetics of indirect photoluminescence corresponds to single-exciton recombination
in the presence of a random potential in the plane of the double quantum wells. The variation of the nonradiative recombination
time is discussed in terms of the variation of the transport of indirect excitons to nonradiative recombination centers, and
the variation of the radiative recombination time is discussed in terms of the variation of the population of optically active
excitonic states and the localization radius of indirect excitons. The photoluminescence kinetics of indirect excitons, which
is observed in the studied GaAs/AlxGa1−x
As double quantum wells for which the random potential has a large amplitude, is qualitatively different from the photoluminescence
kinetics of indirect excitons in AlAs/GaAs wells and GaAs/AlxGa1−x
As double quantum wells with a random potential having a small amplitude. The temporal evolution of the photoluminescence
spectra in the direct and indirect regimes is studied. It is shown that the evolution of the photoluminescence spectra corresponds
to excitonic recombination in a random potential.
Zh. éksp. Teor. Fiz. 115, 1890–1905 (May 1999) 相似文献
4.
Yasuo Oka 《Physics of the Solid State》1998,40(5):778-780
Excitonic properties and the dynamics are reported in quantum dots (QDs) and quantum wells (QW) of diluted magnetic semiconductors.
Transient spectroscopies of photoluminescence and nonlinear-optical absorption and emission have been made on these quantum
nanostructures. The Cd1−x
MnxSe QDs show the excitonic magnetic polaron effect with an increased binding energy. The quantum wells of the Cd1−x
MnxTe/ZnTe system display fast energy and dephasing relaxations of the free and localized excitons as well as the tunneling process
of carriers and excitons in the QWs depending on the barrier widths. The observed dynamics and the enhanced excitonic effects
are the inherent properties of the diluted magnetic nanostructures.
Fiz. Tverd. Tela (St. Petersburg) 40, 846–848 (May 1998)
Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor. 相似文献
5.
Summary An attempt is made to study the effective electron mass in quaternary alloys, taking a In1−x
Ga
x
As
y
P1−y
lattice matched to InP, by using the three-band Kane model under different physical conditions,e.g. bulk specimens, magnetic quantization, cross-field configuration, quantum well, electric-field-aided quantum well, magnetic-field-aided
quantum well, quantum well under cross fields, quantum well wires, electric-field-aided quantum well wires, magnetic-field-aided
quantum well wires and quantum well wires under cross fields by formulating the respective expressions. We have plotted the
effective Fermi level mass with various physical variables under different conditions. In the presence of a quantizing magnetic
field the effective mass depends on the spin splitting of Landau levels due to the spin-orbit splitting parameter of the valence
bands. Under cross-field configuration and the various quantum confined low-dimensional systems, the effective masses depend
on the respective quantum numbers in addition to the Fermi energies even for parabolic models because of the inherent features
of such systems. In addition, the corresponding results for relatively wide-gap materials have also been obtained from our
generalized formulations under certain limiting conditions. 相似文献
6.
A.L. Morales N. Raigoza E. Reyes-Gmez J.M. Osorio-Guilln C.A. Duque 《Superlattices and Microstructures》2009,45(6):590-597
Double quantum well heterostructures are quite important for the exploration of correlated electron states in two-dimensional systems. By using the variational procedure, within the effective-mass and parabolic-band approximations, the effects of both electric field and hydrostatic pressure on the shallow-donor-impurity related polarizability and photoionization cross-section in GaAs–Ga1−xAlxAs double asymmetric quantum wells are presented. The electric field is considered to be applied along the growth direction. It is found that the impurity binding energy and polarizability can be tuned by means of an applied external electric field or hydrostatic pressure in asymmetric double quantum wells, a behavior which could be used in the design and construction of semiconductor devices. The photoionization cross-section magnitude increases as the pressure and applied electric field are increased, except beyond the Γ–X crossover in the barrier material, where a decrease of the photoionization cross-section is expected due the smaller confinement of the impurity wave function. 相似文献
7.
Summary We calculate the binding energy of a two-dimensional exciton for a set of states labelled by the quantum numberm associated to the angular momentum in the direction perpendicular to the surface. The Fr?hlich electron-phonon and hole-phonon
interactions are taken into account. The statem=0 is more bound with respect to that obtained by the Wannier exciton theory with the screening given by the static dielectric
constant and the reduced mass calculated by the electron and hole polaronic masses. The opposite effect is found for the statem=1,2,... Whenm becomes large, the hydrogenic series is recovered with the screening and reduced mass defined above. Our results are compared
with the experimental data concerning exciton luminescence GaAs/Al
x
Ga1−x
As, CuCl/CaF2 and CdTe/Cd1−x
Zn
x
Te quantum wells.
The authors of this paper have agreed to not receive the proofs for correction. 相似文献
8.
K. Mathan Kumar A. John Peter C. W. Lee 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,84(3):431-438
Electronic energies of an exciton confined in a strained
Zn1−x
Cd
x
Se/ZnSe quantum dot have
been computed as a function of dot radius with various Cd content. Calculations have been
performed using Bessel function as an orthonormal basis for different confinement
potentials of barrier height considering the internal electric field induced by the
spontaneous and piezoelectric polarizations. The optical absorption coefficients and the
refractive index changes between the ground state (L = 0) and the first
excited state (L = 1) are investigated. It is found that the optical
properties in the strained ZnCdSe/ZnSe quantum dot are strongly affected by the
confinement potentials and the dot radii. The intensity of the total absorption spectra
increases for the transition between higher levels. The obtained optical nonlinearity
brings out the fact that it should be considered in calculating the optical properties in
low dimensional semiconductors especially in quantum dots. 相似文献
9.
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
10.
Guo-Yu Lan Yang-Wei Lin Zong-Hong Lin Huan-Tsung Chang 《Journal of nanoparticle research》2010,12(4):1377-1388
This article describes the synthesis of highly water-soluble Zn
x
Hg1−x
Se
y
S1−y
quantum dots (QDs) in aqueous solution through a simple photo-assisted reaction between ZnSe QDs and mercury(I) nitrate dihydrate
[Hg2(NO3)2·2H2O]. In order to deduce the optimal synthesis conditions, we varied several parameters, including the concentrations of mercaptosuccinic
acid (MSA) and Hg2(NO3)2·2H2O, the illumination time, and the reaction temperature. When irradiated at temperatures below 80 °C, the ZnSe QDs reacted
with the S2− ions formed rapidly from MSA and the Hg2+ ions formed from Hg2
2+ ions to form Zn
x
Hg1−x
Se
y
S1−y
QDs through a process of photo-etching and surface combination. Under different conditions, we prepared a series of Zn
x
Hg1−x
Se
y
S1−y
QDs that emit fluorescence at the maximum wavelengths ranging from 405 to 760 nm. Inductively coupled plasma-mass spectrometry
and transmission electron microscopy/energy dispersive spectrometry revealed that the content of Hg in the Zn
x
Hg1−x
Se
y
S1−y
QDs was greater when the synthesis was conducted at higher temperature. The Zn0.88Hg0.12Se0.44S0.56 QDs exhibit improved photostability than crude ZnSe QDs and possess long lifetimes (τ1 ~ 38 ns and τ2 ~ 158 ns). 相似文献
11.
V. Ya. Aleshkin A. A. Andronov A. V. Antonov N. A. Bekin V. I. Gavrilenko D. G. Revin B. N. Zvonkov E. R. Lin’kova I. G. Malkina E. A. Uskova 《JETP Letters》1996,64(7):520-524
The infrared radiation from hot holes in InxGa1−x
As/GaAs heterostructures with strained quantum wells during lateral transport is investigated experimentally. It is found
that the infrared radiation intensities are nonmonotonic functions of the electric field. This behavior is due to the escape
of hot holes from quantum wells in the GaAs barrier layers. A new mechanism for producing a population inversion in these
structures is proposed.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 7, 478–482 (10 October 1996) 相似文献
12.
In this paper, we intend to study the effect of variable mass on the binding energy. In
this regard, we apply an analytic expression for position-dependent effective mass in a
cubic quantum dot. Then, we obtain the binding energies of a shallow donor in the quantum
dot of GaAs/Al
x
Ga1−x
As using a
variational procedure within the effective mass approximation. Calculations are presented
with a constant effective mass and position-dependent effective mass. It is found that (i)
the binding energy decreases as the dot length increases in both the cases of constant and
variable masses, (ii) an increase of binding energy is observed when the spatially varying
mass is included, and (v) the binding energy shows complicated behavior when the
position-dependent mass is included for the small dot size
L ≤ 130 ?. 相似文献
13.
S.-g. Zhu J.-j. Shi S. Zhang M. Yang Z.-q. Bao M. Zhang 《Applied physics. B, Lasers and optics》2011,104(1):105-111
In order to give an atomic level understanding of the light emission mechanism and seek In distribution patterns closely related
to the elusive electron localization centers, we optimize the crystal structure of zinc blende In
x
Ga1−x
N (0≤x≤1) alloys with different In distributions and investigate their electronic structures using first-principles calculations.
Our results show that In
x
Ga1−x
N forms a random alloy, in which several-atom In–N clusters and In–N chains can exist stably with a high concentration due
to their small formation energy. These In–N clusters and chains form more easily in zinc blende structure than in wurtzite
structure. The band gap of zinc blende In
x
Ga1−x
N alloys insensitively depends on the In distribution. Moreover, we find that both small In–N clusters and straight In–N chains
with three or more In atoms, acting as radiative recombination centers, highly localize the electrons of the valence band
maximum state and dominate the light emission of Ga-rich In
x
Ga1−x
N alloys. The strains of In
x
Ga1−x
N layers can enhance the electron localization in In
x
Ga1−x
N/GaN strained quantum wells. Our results are in good agreement with experiments and other calculations. 相似文献
14.
M. V. Kochiev N. N. Sibeldin M. L. Skorikov V. A. Tsvetkov 《Bulletin of the Russian Academy of Sciences: Physics》2012,76(2):218-220
The effect of the excitation level on the dynamics of heavy-hole exciton photoluminescence in tunneling-isolated GaAs/Al
x
Ga1 − x
As (x = 0.05) shallow quantum wells at temperatures of 5 to 70 K is investigated. It is shown that the exciton lifetimes depend
strongly on the excitation level, while the activation energies characterizing the thermal escape of nonequilibrium charge
carriers from the wells virtually do not. 相似文献
15.
C. A. Duque M. E. Mora-Ramos E. Kasapoglu H. Sari I. Sökmen 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,81(4):441-449
In this work are studied the intense laser effects on the impurity states in GaAs-Ga1−
x
Al
x
As quantum wells under applied electric and magnetic fields. The electric field is taken oriented along the growth direction
of the quantum well whereas the magnetic field is considered to be in-plane. The calculations are made within the effective
mass and parabolic band approximations. The intense laser effects have been included through the Floquet method by modifying
the confinement potential associated to the heterostructure. The results are presented for several configurations of the dimensions
of the quantum well, the position of the impurity atom, the applied electric and magnetic fields, and the incident intense
laser radiation. The results suggest that for fixed geometry setups in the system, the binding energy is a decreasing function
of the electric field intensity while a dual monotonic behavior is detected when it varies with the magnitude of an applied
magnetic field, according to the intensity of the laser field radiation. 相似文献
16.
Energy characteristics of Si1–x
Ge
x
–Si quantum-size structures with single quantum wells were calculated numerically based on a four-band k·p method. Analytical expressions for the Luttinger parameters are obtained as functions of the component composition of Si1–x
Ge
x
compounds. Analytical expressions for the energy ħω of optical band-to-band transitions are obtained in an effective mass
approximation and agree well with numerical calculations by the k·p method. This allows one to determine accurately a range of changes while varying the component compositions and thickness
of the active and barrier layers. 相似文献
17.
Summary Thek-conserving selection rule in the electron-hole recombination is investigated by intensity-dependent photoluminescence measurements
inn-type modulation-doped Ga
x
In1−x
As−Al
y
In1−y
As single quantum wells intentionally doped with Be acceptors in the well centre. Thek-non-conserving recombination process involves electrons with momentum up to the Fermi edge and holes localized on the Be
acceptors. The transition from a one-component electron plasma to a two-component electron-hole plasma is studied by comparing
the experimental results with theoretical line shape models. The density-dependent band gap renormalization is determined
for the one-component and the two-component electron-hole plasma. The obtained results are found to agree well with recent
theoretical calculations. 相似文献
18.
E. V. Bogdanov N. B. Brandt N. Ya. Minina S. S. Shirokov 《Moscow University Physics Bulletin》2011,66(6):568-573
The band structure, size quatized levels, and wave functions in the conduction and valence bands of strained n-Al
x
Ga1 − x
As/GaAs
y
P1 − y
/p-Al
x
Ga1 − x
As (y = 0.84) heterostructures are calculated numerically upon a uniaxial compression along the [110] direction. The calculation
indicates a sublinear increase of the effective optical gap in the GaAs0.84P0.16 quantum well, strong mixing of states of light and heavy holes, and merging of the corresponding ground states in the quantum
well of the valence band under a pressure of 4.5–5 kbar. The calculation of matrix elements of the electron-photon interaction
operator for a system of possible interband transitions permits one to determine the optical gain for the TE and TM modes.
The increase in this coefficient by two to fourfold under uniaxial compression agrees with the previously published experimental
data on the increase of the electroluminescence intensity. 相似文献
19.
I. G. Aksyanov A. V. Kudinov Yu. G. Kusraev B. P. Zakharchenya T. Wojtowicz G. Karczewski J. Kossut 《Physics of the Solid State》1999,41(5):820-823
A study is reported of the anisotropy in magnetic-field-induced linear polarization in (001) CdTe/Cd1−x
MnxTe quantum wells. The observed limiting anisotropy is shown to be due to the low C
2v
symmetry of the quantum well. The relations obtained for the C
2v
point group are in a good agreement with experiment. Considered on the microscopic scale, the effect is associated with the
heavy-hole g-factor anisotropy in the well plane.
Fiz. Tverd. Tela (St. Petersburg) 41, 903–906 (May 1999) 相似文献
20.
A. B. Dzyubenko 《Journal of Experimental and Theoretical Physics》1998,86(4):790-797
A theory of far-infrared (FIR) magneto-optical intraband s→p
± transitions of direct and indirect excitons in semiconductor coupled double quantum wells has been developed. The case of
symmetric strained InxGa1−x
As/GaAs quantum wells with nondegenerate valence band in the regime of both narrow and wide barriers has been analyzed. The
energies and dipole matrix elements of transitions between the ground s and excited p
± states in a quantizing magnetic field B>2 T and electric field ℰ perpendicular to the quantum well plane have been studied. The regimes of direct (in a weak electric
field) and indirect (in a strong electric field) transitions, and the transition between the direct and indirect regimes,
have been investigated.
Zh. éksp. Teor. Fiz. 113, 1446–1459 (April 1998) 相似文献