Optical detection of magnetoplasma resonances in indirect-gap AlAs/AlGaAs quantum wells

Magnetoplasma excitations in AlAs/AlGaAs quantum wells, characterized by strong anisotropy in the effective mass of two-dimensional electrons, are investigated using the optical detection of resonance microwave absorption. This technique is used for the first time for an indirect-gap semiconductor. It is found that the magnetic dispersion of the cyclotron magnetoplasma mode deviates significantly from the theoretically expected behavior. This may be related to the considerably more pronounced manifestation of retardation effects in two-dimensional systems with an anisotropic energy spectrum.