Electrons, Phonons and their Interactions in Novel Modulation Doped GaAs/AlAs Based Quantum Wells

摘要

The lowest energy interband transitions in AlGaAs/AlAs quantum wells involve electrons localized in the AlAs x-valleys and holes confined in the AlGaAs layers. These transitions are indirect in both real as well as in kappa- space and are accompanied by strong replicas of the GaAs and AlAs phonons. When a magnetic field is applied perpendicular to the layers a large reduction in the recombination intensity is observed. This reduction is attributed to magnetic field induced localization of the carriers which results in a reduction of the electron-hole wavefunction overlap. We have also studied photoluminescence spectra from type-II, n-type, modulation doped GaAs/AlAs quantum wells due to radiative recombination of electrons localized in the AlAs x-valleys with holes confined in the GaAs layers. In the presence of a magnetic field the emission spectra exhibit features associated with transitions among the AlAs x-valley Landau levels and photo-injected holes. The slopes of these transitions yield an effective mass m* = 0.44 for the electrons.