Effect of an in-plane magnetic field on the photoluminescence spectrum of modulation-doped quantum wells and heterojunctions

Abstract

The photoluminescence (PL) spectrum of modulation-doped GaAs/AlGaAs quantum wells (MDQW) and heterojunctions (HJ) is studied under a magnetic field (B ) applied parallel to the two-dimensional electron gas (2DEG) layer. The effect of B strongly depends on the electron-hole separation (d eh ), and we revealed remarkable B -induced modifications of the PL spectra in both types of heterostructures. A model considering the direct optical transitions between the conduction and valence subband that are shifted in k-space under B , accounts qualitatively for the observed spectral modifications. In the HJs, the PL intensity of the bulk excitons is strongly reduced relatively to that of the 2DEG with increasing B . This means that the distance between the photoholes and the 2DEG decreases with increased B , and that free holes are responsible for the hole-2DEG PL.

Correlated electron-hole transitions in bulk GaAs and GaAs-(Ga,Al)As quantum wells: effects of applied electric and in-plane magnetic fields

“…In the inset of Fig. 3, the present theoretical results are compared with fair agreement with recent experimental data [11]. Of course, for high values of the applied magnetic field, a reliable calculation should involve a more realistic type of wave function which would appropriately take into account magnetic-field induced anisotropic effects.…”

“…Combined theoretical and experimental studies from Ashkinadze et al [11] for the effect of an in-plane magnetic field on the photoluminescence (PL) spectrum of modulation-doped heterostructures have suggested that there are remarkable spectral modifications of the PL spectra in both modulationdoped QWs and high-quality heterojunctions, due to Binduced modifications in the direct optical transitions in QWs, and effects on the free holes in heterojunctions, respectively. Also, studies [12] on the magnetic-field effects on indirect excitons in coupled GaAs-(Ga,Al)As QWs reveal that the exciton effective mass is enhanced as the growth-direction magnetic field increases and, at high fields, it becomes larger than the sum of the e and h masses, suggesting that a magnetoexciton is an excitation with effective mass determined by the coupling [5] between the exciton center of mass (CM) motion and internal structure rather than by the masses of its constituents.…”

“…Results for the calculated z e − z h average e − h distance in the z-direction [Figs. 1(c) and 1(f)] are as follows: As shown, z e − z h = 0 for ∆ = 0 and E = 0 for a finite value of the magnetic field, [11].…”

“…Work on exciton properties have been recently performed both experimentally [1-4] and theoretically [5][6][7][8][9][10][11][12]. Luminescence measurements in GaAs-Ga 1−x Al x As double quantum wells (QWs) under inplane magnetic fields [1,2] have concluded that the dominating radiative recombination of localized indirect excitons does not allow one to observe the quenching of the spatially indirect exciton luminescence and the quadratic shift of their energy under in-plane magnetic fields, with the consequence that the possibility of an exciton dispersion engineering would then be limited in these kinds of samples.Combined theoretical and experimental studies from Ashkinadze et al [11] for the effect of an in-plane magnetic field on the photoluminescence (PL) spectrum of modulation-doped heterostructures have suggested that there are remarkable spectral modifications of the PL spectra in both modulationdoped QWs and high-quality heterojunctions, due to Binduced modifications in the direct optical transitions in QWs, and effects on the free holes in heterojunctions, respectively. Also, studies [12] on the magnetic-field effects on indirect excitons in coupled GaAs-(Ga,Al)As QWs reveal that the exciton effective mass is enhanced as the growth-direction magnetic field increases and, at high fields, it becomes larger than the sum of the e and h masses, suggesting that a magnetoexciton is an excitation with effective mass determined by the coupling [5] between the exciton center of mass (CM) motion and internal structure rather than by the masses of its constituents.…”

“…When the electron and hole carriers are confined in the same region of the direct space and in the same point of the inverse k-space, the exciton is called a direct exciton; alternatively, if the carriers are confined in different regions of the direct space and/or in different points of the inverse k-space the exciton is termed as an indirect exciton. Work on exciton properties have been recently performed both experimentally [1][2][3][4] and theoretically [5][6][7][8][9][10][11][12]. Luminescence measurements in GaAs-Ga 1−x Al x As double quantum wells (QWs) under inplane magnetic fields [1,2] have concluded that the dominating radiative recombination of localized indirect excitons does not allow one to observe the quenching of the spatially indirect exciton luminescence and the quadratic shift of their energy under in-plane magnetic fields, with the consequence that the possibility of an exciton dispersion engineering would then be limited in these kinds of samples.…”