Absorption and reflection experiments on high-mobility 2DEGs in the regime of microwave-induced resistance oscillations

We have performed microwave absorption and near-field reflection experiments on a high mobility GaAs/AlGaAs heterostructure for the same conditions for which Microwave-Induced Resistance Oscillations (MIROs) are observed. It is shown that the electrodynamic aspect of the problem is important in these experiments. In the absorption experiments a broad CR line was observed due to a large reflection from the highly conductive electron gas. There were no additional features observed related to absorption at harmonics of the cyclotron resonance. In near-field reflection experiments a very different oscillation pattern was revealed when compared to MIROs. The oscillation pattern observed in the reflection experiments is probably due to plasma effects occurring in a finite-size sample. The whole microscopic picture of MIROs is more complicated than simply a resonant absorption at harmonics of the cyclotron resonance. Nevertheless, the experimental observations are in good agreement with the model by Durst et al. involving the photo-assisted scattering in the presence of a crossed magnetic field and dc bias. The observed damping factor of MIROs may be attributed to a change in the electron mobility as a function of temperature. MIROs may be considered as a light-induced drift effect, a broad class of phenomena associated with a light-induced asymmetry in the velocity distribution function.