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 $30\ensuremath{\le}f\ensuremath{\le}50\phantom{\rule{0.28em}{0ex}}\text{GHz}$ with source power $0\ensuremath{\le}P\ensuremath{\le}4\phantom{\rule{0.28em}{0ex}}\text{mW}$ served to photoexcite the high mobility ($\ensuremath{\simeq}{10}⁷\phantom{\rule{0.28em}{0ex}}{\text{cm}}²/\text{V}\phantom{\rule{0.16em}{0ex}}\text{s}$) 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 $2.3<{\ensuremath{\omega}}_c/\ensuremath{\omega}\ensuremath{\le}5.2$, where ${\ensuremath{\omega}}_c=eB/{m}^*,\phantom{\rule{0.28em}{0ex}}\ensuremath{\omega}=2\ensuremath{\pi}f,\phantom{\rule{0.28em}{0ex}}B$ 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 (${T}_e$) as a function of $P$ and $T$. Theory has proposed that, in the ${\ensuremath{\omega}}_c/\ensuremath{\omega}\ensuremath{\ge}1$ regime, both the electron temperature and radiation energy absorption rate (${S}_p$) exhibit relatively small response, while in the ${\ensuremath{\omega}}_c/\ensuremath{\omega}\ensuremath{\le}1$ regime, both ${T}_e$ and ${S}_p$ 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.