Electronic properties of quantum wells in perturbing fields

Abstract

StudiesStudies of the response of excitonic transitions in quantum wells to external perturbations have proven useful in understandingunderstanding the electronic properties of quantum wells. This paper discusses the use of two such perturbations, electric fieldsfields and uniaxial stress, in photocurrent and photoluminescence excitation spectroscopy measurements on GaAs/AlxGa1-xAs quantum wells. When an electric field is present in a square quantum well, forbidden excitonic transitions become visible. The excitons also exhibit a Stark shift to lower energies. Since the Stark shifts for different excitons are not the same, it is possible to tune the energy separations between the excitons. By applying electric fields to a 160 áell, an anticrossing between the excited states of the first heavy hole exciton and the Is ground state of the first light hole excitonexciton has been observed. The effect of a uniaxial stress on a quantum well is found to depend strongly upon the axis along which the stress is applied. This is in contrast to bulk GaAs. The application of a uniaxial stress to a quantum well can help determine the valence band symmetry of a particular exciton, since heavy and light hole excitons exhibit different energyenergy shifts in a stress. This fact has been used in conjunction with polarization and electric field dependent measurementsments to identify exciton peaks which arise from mixing between the second heavy and first light hole valence subbands. © 1987, SPIE.