Dimensional magnetoplasma resonance detected by free-exciton photoluminescence in modulation-doped GaAs/AlxGa1-xAs heterojunctions

We studied the effect of microwave (mw) irradiation on the low-temperature photoluminescence (PL) of high-quality, modulation-doped, wide GaAs/AlxGa1- xAs heterojunctions (HJ's) containing a two-dimensional electron gas (2DEG) , in the density range of (0.9-4)x 10(11) cm(-2). The PL arises from excito ns that recombine radiatively in the GaAs buffer layer, far from the 2DEG w hich is confined close to the GaAs/AlxGa1-xAs interface. We observe that th e exciton PL is affected by a mw heating of the 2DEG: the mw-induced PL int ensity change increases with increasing 2DEG density as well as under a per pendicular magnetic field that corresponds to the 2DEG dimensional magnetop lasma resonance (DMPR) condition. Moreover, the exciton PL intensity shows a bistability at magnetic field strengths that are close to those observed in the DMPR mw absorption. The mw-induced PL modulation effects are interpr eted as being due to the interaction of the excitons with low-energy, balli stically propagating acoustic phonons that are emitted by the mw-heated 2DE G. The exciton PL quenching is associated with an exciton drag by the phono n flux towards the opposite l-IJ interface where the excitons recombine non radiatively. The rate of phonon emission is determined by the 2DEG state, a nd thus the exciton PL responds to the changes of the 2DEG parameters.