Electron heating induced by microwave photoexcitation in the GaAs/AlGaAs two-dimensional electron system

We examined the influence of microwave radiation on both the amplitude of Shubnikov--de Haas (SdH) oscillations and the null field longitudinal magnetoresistance at liquid helium temperatures, in GaAs/AlGaAs Hall bar devices. Microwave radiation over the frequency range 30≤f≤500.28em0exGHz with source power 0≤P≤40.28em0exmW served to photoexcite the high mobility (10⁷0.28em0excm²/V0.16em0exs) two-dimensional electron system (2DES) as magnetoresistance traces were obtained as a function of the microwave power P and temperature T. Line-shape study of SdH oscillations has been carried out over the span 2.3<ωc/ω≤5.2, where ωc=eB/m*,0.28em0exω=2πf,0.28em0exB is the magnetic field, m* is the effective mass, and f is the microwave frequency. Here, fits of the SdH line shape served to determine the electron temperature (Tₑ) as a function of P and T. Theory has proposed that, in the ωc/ω≥1 regime, both the electron temperature and radiation energy absorption rate (Sₚ) exhibit relatively small response, while in the ωc/ω≤1 regime, both Tₑ and Sₚ are enhanced and exhibit oscillatory behavior. We compare the experimental results with these theoretical predictions, and comment upon the relative role of electron heating in the microwave photoexcited high-mobility 2DES.