Observation of Landau levels and excitons at room temperature inIn0.53Ga0.47As

Abstract

We report on magneto-optical Kerr-ellipticity measurements with different In 0.53 Ga 0.47 As/InP multiquantum-wells at room temperature. These samples are grown with nominally the same sample parameters, except for the barrier thickness, which for one sample is small enough for a coupling between the quantum wells. The spectral range covered the quantum-well interband transitions of the electron-heavy-hole ground states. The magneto-optical spectra show a number of oscillations, whose spectral position depends on the magnetic-field strength. For model calculations, Lorentzian line shapes for the off-diagonal element of the dielectric tensor have been used. Magneto-optical interference effects are carefully discussed. For small magnetic fields, the shift of the ground state shows a diamagnetic behavior. For the coupled quantum well a transition into the high-field regime can be seen at BϷ9 T. Due to the higher exciton energy for the uncoupled system, high-field behavior occurs only at fields beyond the range of the present experiments. Model calculations allow us to estimate from the shift of the ground state (1s), the exciton binding energy and the dimensionality of the system. According to these calculations the uncoupled sample shows a more 2D-like ͑where 2D is two-dimensional͒ behavior, while the coupled system is more 3D like. The higher levels, however, are typical for Landau splitting. For these the excitonic effect is negligible compared to the Landau shift. In our experiments, we were able to trace the oscillations up to 200 meV above the band gap of unstrained In 0.53 Ga 0.47 As bulk material. This allows us to determine the energy dependence of the reduced effective mass at room temperature. Using the three-band Kane model for the calculation of the electron effective mass, we find that the hole effective mass in In 0.53 Ga 0.47 As quantum wells is significantly lower than in bulk material.

Electric and Magnetic Field Effects on Optical Properties of Excitons in Parabolic Quantum Wells and Quantum Dots

“…We can observe that the peaks are displaced by the field and good agreement is obtained with the observed experimental trend of Ref. [3] (Fig. 3).…”

“…The influence of the strong applied magnetic field becomes evident when high magnetic fields, up to 45 T, are used, as it has been shown in recent magnetoluminescence spectra of InGaAs/GaAs QDs [1,2]. Similar results have been obtained for InGaAs/InP [3] and AlGaAs/InGaAs [4] QWs. The diamagnetic shift and the excitonic binding energy increase with the magnetic field.…”

“…Having the eigenfunctions and the corresponding eigenvalues, we can solve the constitutive equations (3). We separate the time dependent part and expand the spacialdependent part in terms of the eigenfunctions (10)…”

Optical properties of magnetoexcitons in double quantum dots

“…Such effect was observed for quantum wells (see, for example, Ref. [19]), quantum dots [20] and quantum disks [21]. It was also observed for a system of InP/InGaP two vertically stacked dots [22,23], which corresponds to the situation discussed above.…”

Effects of a longitudinal magnetic field on spin injection and detection in InAs/GaAs quantum dot structures

“…In comparison, XH and XL only show a small and quadratic shift towards higher energies with increasing field, confirming their excitonic character. [17] The energy distance between the merging of the LLs at zero field and the exciton line XH yields an exciton binding energy of 3.5 meV. From the LL transitions, we deduce an in-plane reduced effective mass of the electron-hole pair involving the hh VB of the WL to be 0.059 m 0 , 0.052 m 0 and 0.058 m 0 for SQD, DQD1 and DQD2, respectively.…”