Coherent magnetotunneling in coupled quantum wells for different Landau levels (original) (raw)
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Superlattices and Microstructures, 1987
We investigated theoretically the effect of in-plane magnetic fields up to 20 Testa on the quantum states of electrons and holes confined in quantum wells (QWs) with a non-flat bottom in GaAs-A~gaAs heterostructures Two kinds of QWs were studied: a) QWs bent by the Coulom~ interaction in the 2D electron gas in modulation-doped superlattices and b) QWs grown with a triangle-shaped bottom throught controlled grading of the A~ concentration in the QW region of undoped heterostructures
Physical Review B, 1987
The effect of in-plane magnetic fields B up to 20 T on the electron-hole gas confined in symmetric (SQW's) and asymmetric (AQW's) quantum wells in n-type CsaAs-Al Gal "As heterostructures is theoretically investigated by a self-consistent numerical solution of the Poisson and Schrodinger 0 equations. Quantum-well widths L =75, 150, 225, and 300 A and two-dimensional electron densities N, =0, 2. 5&10", 5.0&&10" and 7.5&(10" cm are considered. The magnetic field produces noticeable changes in the charge distribution inside the QW and drastic changes in the energy dispersion c(k) of both electrons and holes in the in-plane direction perpendicular to B. The diamagnetic shift in the electron-hole recombination energy is shown to increase with increasing L and decreasing N,. For L"&225 A and N,)2.5&&10"cm the energy dispersion c.l(k) of the first conduction subband in the SQW presents, at high fields, a double-minimum character so that the gap becomes indirect. For the AQW the symmetry e, (k)=e, (k) is broken and the gap is also indirect. Recent photoluminescence measurements are discussed in relation to the present calculations.
Oscillatory behavior of magneto-optical interband emissions in asymmetric quantum well structures
Superlattices and Microstructures, 1997
We report on the oscillatory behavior of the photoluminescence intensity from asymmetric AlGaAs/InGaAs/GaAs quantum well structures in the presence of a perpendicular magnetic field. Two distinct photoluminescence peaks originating from transitions from the ground (e 1) and the first excited (e 2) electronic states to the heavy hole state (hh 1) are observed. The opposite phase of the oscillations shows clearly the competitive process between the transitions from the ground and first excited states. Electron transfer mechanisms cannot explain the origin of these oscillations. The optical oscillations emerge from changes in the effective electron-hole interaction.
1987
We present a self-consistent calculation of the electronic structure of an Al"Gal-"As-GaAs-Al, Ga~"As selectively doped single quantum well (QW) 500 4 wide under a high magnetic field applied perpendicular to the interfaces of confinement of the two-dimensional electron gas (2D EG). The calculation shows that the energy diff'erence between electronic subbands changes with the magnetic field when three electronic subbands are occupied. This eA'ect is related to the heterostructure character of the QW considered. Moreover, it is shown that these variations are related to the oscillatory behavior of the 2D EG's charge density. Our results seem to be confirmed by the available experimental data found in the literature, and we propose additional experiments in order to further verify the results obtained.
Quantum oscillations of spin polarization in a GaAs/AlGaAs double quantum well
Physical Review B, 2012
We employ the circular-polarization-resolved magnetophotoluminescence technique to probe the spin character of electron and hole states in a GaAs/AlGaAs strongly coupled double-quantum-well system. The photoluminescence (PL) intensities of the lines associated with symmetric and antisymmetric electron states present clear out-of-phase oscillations between integer values of the filling factor ν and are caused by magnetic-field-induced changes in the population of occupied Landau levels near to the Fermi level of the system. Moreover, the degree of circular polarization of these emissions also exhibits the oscillatory behavior with increasing magnetic field. Both quantum oscillations observed in the PL intensities and in the degree of polarizations may be understood in terms of a simple single-particle approach model. The k · p method was used to calculate the photoluminescence peak energies and the degree of circular polarizations in the double-quantum-well structure as a function of the magnetic field. These calculations prove that the character of valence band states plays an important role in the determination of the degree of circular polarization and, thus, resulting in a magnetic-field-induced change of the polarization sign.
Solid State Communications, 1995
We investigated the current-voltage I(V) characteristics of GaAs/AlAs double-barrier heterostructures. A fine periodic structure of the resonant tunnel current has been revealed. We attribute it to a sequence of the collective excitations, presumably of the coupled plasmon-phonon type, that are induced in the heavily doped collector region by hot electrons which escape from the quantum well. An oscillatory structure appears also in the valley regions of the I(VJ curve under a high magnetic field parallel to the current. It is due to the off-resonance tunnelling between the Landau-quantized states of the emitter and quantum well. Particular phonon-assisted processes in the tunnelling have been identified.
We h a ve i n vestigated the in uence of an uniform electric eld, applied in the growth direction, and an uniform magnetic eld, perpendicular to this direction, on the resonant tunneling of electrons in a system formed by t wo asymmetric quantum wells separated by a thin barrier. The semiconductor heterostructure is considered in the e ective mass approximation and one band model. The method we h a ve used to calculated the electronic structure is based on the solution of the time-dependent S c hr odinger equation using the split-operator technique. The tunneling dynamics in the resonance condition is studied using the time evolution of a wave-packet from which w e determine the tunneling time. A comparison with recent experimental data is presented.
International Journal of Quantum Chemistry, 1986
The effect of in-plane magnetic fields B up to 20 T on the carriers confined in symmetric (saw) and asymmetric (AQW) quantum wells in n-type GaAs-Ae,Gal-.As superlattices is investigated by a self-consistent aumerical solution of the Poisson plus Schrodinger equations. Quantum-well widths L, = 75 A, 150 A, 225 A, and 300 A and 2D electron densities N , = 0, 2.5, 5.0, and 7.5 (10" cm-*) are considered. The diamagnetic shift in the electron-hole recombination energy is shown to increase with increasing L, and decreasing N,. For L, 2 225 8, and N , 2 2.5 x 10" cm-* the energy dispersion el(& of the first conduction subband in the SQW presents, at high fields, a double-minimum character so that the gap becomes indirect. For the AQW the symmetry r l (k) = r l (-k) is broken, and the gap is also indirect. Recent photoluminescence measurements are discussed in relation to the present calculations.