Mechanism of microwave-induced photoluminescence modulation and optically detected resonances due to a two-dimensional electron gas in a heterostructure

Abstract

The effect of pulsed microwave ͑mw͒ irradiation ͑at 36 GHz͒ on the photoluminescence ͑PL͒ of modulationdoped GaAs/AlGaAs quantum wells ͑MDQWs͒ containing a two-dimensional electron gas ͑2DEG͒ is studied by time-resolved spectroscopy at an ambient temperature of 2 K. The temporal response of the twodimensional electron-hole PL to a short mw pulse reveals remarkable PL intensity kinetics with overshoots and a long decay time ͑Ͼ10 ns͒ 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 ͑ODRs͒ 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 excitons͒. This interaction constitutes the underlying mechanism of the mw-induced ODRs observed in heterostructures containing a 2DEG.

Imaging of magnetoplasmons excited in a two-dimensional electron gas

“…1b,c are due to mw-heating of the 2D-electrons. [7][8][9][18][19][20] Fig . 2 shows the PL spectral variations along the excitation strip (y-direction) as imaged through the spectrometer.…”