Effect Of In-plane Magnetic Field Research Articles

Effect of in-plane magnetic fields on the interband optical absorption spectra of GaAs-(Ga,Al)As superlattices

A theoretical study of the effects of in-plane magnetic fields on the interband optical absorption spectra of GaAs-(Ga,Al)As superlattices is presented. The envelope wave functions were obtained by an expansion in terms of sine functions. Whereas in the bulk case the selection rule Δn=0 for transitions between Landau levels is satisfied, the presence of the superlattice potential makes possible the occurrence of interband transitions with Δn≠0. The 19 T calculated interband peaks in the absorption spectrum agrees quantitatively well with the main experimental peaks by Belle, Maan, and Weimann.

Effect of in-plane magnetic fields on the electronic structure and photoluminescence spectra in doped semiconductor quantum wells

The effect of in-plane magnetic fields on the carrier energy dispersion, mass enhancement and the photoluminescence line-shape is investigated in semiconductor quantum wells. Exact results are obtained for parabolic quantum wells. An accurate numerical method applicable for arbitrary confinement potentials is introduced. This technique, based on a plane-wave basis set, is applied to the square-well potential. Minimum-photoluminescence-energy data are presented as a function of magnetic field. The theoretical results yield reasonable agreement with the data.

Electronic subbands at GaAsA [formula omitted]GaAs heterojunctions in parallel magnetic fields

We investigated theoretically the effect of in-plane magnetic fields up to 20 T on the quasi-two dimensional (2D) electron gas confined in inversion layers of p-type GaAs at GaAsA l GaAs heterojunctions. The calculations are based on a simultaneous self-consistent solution of the Poisson and Schrödinger equations in the effective mass approximation and including exchange correlation effects. The systems were considered with different values for the 2D electron density (N S) and for the depletion charge density N dep = 5.0 × 10 10 cm −2 in the GaAs channel. The energy dispersion ϵ(k) for the in-plane direction perpendicular to the field is much affected, presenting a diamagnetic shift and a displacement of the single extremum k = 0. The respective charge density is also disturbed. A strong nonparabolicity in ϵ(k) is obtained changing drastically the effective mass of the system at the Fermi level for high magnetic fields.

The effect of in-plane magnetic fields on the quantum states of carriers in quantum wells in GaAsA [formula omitted]GaAs heterostructures

We investigated theoretically the effect of in-plane magnetic fields up to 20 Tesla on the quantum states of electrons and holes confined in quantum wells (QWs) with a non-flat bottom in GaAsA l GaAs heterostructures. Two kinds of QWs were studied: a) QWs bent by the Coulomb 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 l concentration in the QW region of undoped heterostructures. In this last kind of QW two special cases were treated: the symmetric QW (SQW) in which the conduction band (CB) edge has a maximum in the middle of the well and the asymmetric QW (AQW) in which the CB edge is at one border of the well. The energy dispersion ε(k) for the in-plane direction k perpendicular to the field is considerably affected by the field and for broader QWs the effect becomes dramatic. For the QWs of both kinds the system becomes indirect-gap type at high fields and for AQWs the symmetry ε(k) = = ε(−k) is broken.

Photoluminescence study of two-dimensional carriers in the presence of in-plane magnetic fields

We have measured the effect of in-plane magnetic fields on the photoluminescence of 2D carriers confined in a modulation-doped GaAsAlGaAs MQW heterostructure. The most dramatic effect is a large increase, and eventual saturation at high fields, of the intensity of radiative recombination at interface acceptors (binding energy ∼ 10 meV). We explain this as a result of field-induced spreading of the confined wave functions toward the barriers. We show this behavior to be qualitatively consistent with an analytically soluble model which combines the in-plane magnetic field with harmonic quantum well confinement to give a 1D composite oscillator. The low field spreading is due to linear displacement of the oscillator centers with B; at higher fields the magnetic field confinement shrinks the wave functions, and they recede from the interfaces. We observe also a diamagnetic shift and a spectral narrowing of the band-to-band recombination. These effects are confirmed quantitatively with the composite oscillator model.

The behavior of carriers in quantum wells in GaAs-A?xGa1 ?xAs superlattices under in-plane magnetic fields

The effect of in-plane magnetic fields B up to 20 T on the carriers confined in symmetric (SQW) and asymmetric (AQW) quantum wells in n-type GaAs-A𝓁xGa1 – xAs superlattices is investigated by a self-consistent numerical solution of the Poisson plus Schrödinger equations. Quantum-well widths Lw = 75 Å, 150 Å, 225 Å, and 300 Å and 2D electron densities Ns = 0, 2.5, 5.0, and 7.5 (1011 cm−2) are considered. The diamagnetic shift in the electron-hole recombination energy is shown to increase with increasing Lw and decreasing Ns. For Lw ⩾ 225 Å and Ns ⩾ 2.5 × 1011 cm−2 the energy dispersion ϵ1(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 AQWM the symmetry ϵ1(k) = ϵ1(-k) is broken, and the gap is also indirect. Recent photoluminescence measurements are discussed in relation to the present calculations.

Effects of in-plane magnetic field on bubble properties in ion-implanted garnet fims

In the ion-implanted garnet films for hard bubble suppression, there exist planar closure domains associated with bubbles, which are created or annihilated by a rotating in-plane magnetic field. We have investigated the effects of closure domains on magnetic bubble properties in the epitaxial films of (YEuYbCa) 3 (FeGe) 5 - O 12 implanted with Ne+ or H+ ions. Experimental results are summarized as, (1) static coercivity in the H+ implanted film exhibited a 3-fold symmetry, as in the bubble collapse field, in response to the behavior of closure domains when the in-plane field of 40 Oe was rotated. (2) Wall state switching for decreasing in-plane field in the film implanted with 2 \times 10^{14} Ne+/cm2at 100 keV depended on the directions of the in-plane field. When the in-plane field Hp was applied in the [ 11\bar{2} ] direction with the bias field applied in the [111] direction, distinct wall state transitions occured at about Hp=120 Oe, 40 Oe and 10 Oe. When Hp was applied in the [ \bar{1}\bar{1}2 ] direction, however, wall state changed continuously below Hp=120 Oe at which distinct wall state transition occured.