We report the results of a combined microwave polarization-dependence-and power-dependence study of the microwave radiation-induced magnetoresistance oscillations in high mobility GaAs/AlGaAs heterostructure devices at liquid helium temperatures. The diagonal resistance was measured with the magnetic field fixed at the extrema of the radiation-induced magnetoresistance oscillations, as the microwave power was varied at a number of microwave polarization angles. The results indicate a non-linear relation between the oscillatory peak-or valley-magnetoresistance and the microwave power, as well as a cosine square relation between the oscillatory peak-or valleymagnetoresistance and the microwave polarization angle. A simple model is provided to convey our understanding of the observations.

A comparative study of the radiation-induced magnetoresistance oscillations in the high mobility GaAs/AlGaAs heterostructure two dimensional electron system (2DES) under linearly- and circularly- polarized microwave excitation indicates a profound difference in the response observed upon rotating the microwave launcher for the two cases, although circularly polarized microwave radiation induced magnetoresistance oscillations observed at low magnetic fields are similar to the oscillations observed with linearly polarized radiation. For the linearly polarized radiation, the magnetoresistive response is a strong sinusoidal function of the launcher rotation (or linear polarization) angle, θ. For circularly polarized radiation, the oscillatory magnetoresistive response is hardly sensitive to θ.

We examine and compare the diagonal magnetoresistance, R xx , and the photo-voltage induced by microwave (42 ≤ f < 300GHz) and terahertz (f ≥ 300GHz) photoexcitation in the high mobility quasi two-dimensional GaAs/AlGaAs system. The data demonstrate strong radiation-induced magneto-resistance oscillations in R xx to 360GHz. In addition, cyclotron resonance is observed in the photo-voltage to 725GHz. These results show that our high mobility GaAs/AlGaAs 2DES specimens remain photo-active in magnetotransport into the terahertz band.

We demonstrate a strong correlation between the magnetoresistive and the concurrent microwave reflection from the microwave photo-excited GaAs/AlGaAs twodimensional electron system (2DES). These correlations are followed as a function of the microwave power, the microwave frequency, and the applied current. Notably, the character of the reflection signal remains unchanged even when the current is switched off in the GaAs/AlGaAs Hall bar specimen. The results suggest a perceptible microwave-induced change in the electronic properties of the 2DES, even in the absence of an applied current.

Linear polarization angle, θ, dependent measurements of the microwave radiation-induced oscillatory magnetoresistance, R xx , in high mobility GaAs/AlGaAs 2D electron devices have shown a θ dependence in the oscillatory amplitude along with magnetic field, frequency, and extrema-dependent phase shifts, θ 0 . Here, we suggest a microwave frequency dependence of θ 0 (f ) using an analysis that averages over other smaller contributions, when those contributions are smaller than estimates of the experimental uncertainty.