Mechanism Of Microwave-Induced Photoluminescence Modulation And Optically Detected Resonances Due To A Two-Dimensional Electron Gas In A Heterostructure

The effect of pulsed microwave (mw) irradiation (at 36 GHz) on the photoluminescence (PL) of modulation-doped GaAs/AlGaAs quantum wells (MDQWs) containing a two-dimensional electron gas (2DEG) is studied by time-resolved spectroscopy at an ambient temperature of 2 K. The temporal response of the two-dimensional electron-hole PL to a short mw pulse reveals remarkable PL intensity kinetics with overshoots and a long decay time (>10 ns) after the mw pulse terminates. The observed effects are explained by the temporal evolution of the energy redistribution of photoexcited holes. This redistribution is caused by nonequilibrium, long-lived acoustic phonons that are emitted by the mw heated 2DEG and are absorbed by the holes. Optically detected resonances (ODRs) of the 2DEG are observed in both the two-dimensional electron-hole PL band and in the PL line of excitons that are photoexcited in the undoped superlattice adjoining the MDQW. This provides an experimental proof that the emitted acoustic phonons propagate ballistically throughout the entire heterostructure and induce an effective, long range, indirect interaction between the mw heated 2DEG and the holes (as well as with the spatially separated excitons). This interaction constitutes the underlying mechanism of the mw-induced ODRs observed in heterostructures containing a 2DEG.