Dimensional magnetoplasma resonance detected by free-exciton photoluminescence in modulation-dopedGaAs/AlxGa1−xAsheterojunctions

Abstract

We studied the effect of microwave (mw) irradiation on the low-temperature photoluminescence (PL) of high-quality, modulation-doped, wide $\mathrm{GaAs}/{\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$ heterojunctions (HJ's) containing a two-dimensional electron gas (2DEG), in the density range of $(0.9\char21{}4)\ifmmode\times\else\texttimes\fi{}{10}^{11}{\mathrm{cm}}^{\ensuremath{-}2}.$ The PL arises from excitons that recombine radiatively in the GaAs buffer layer, far from the 2DEG which is confined close to the $\mathrm{GaAs}/{\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$ interface. We observe that the exciton PL is affected by a mw heating of the 2DEG: the mw-induced PL intensity change increases with increasing 2DEG density as well as under a perpendicular magnetic field that corresponds to the 2DEG dimensional magnetoplasma 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 interpreted as being due to the interaction of the excitons with low-energy, ballistically propagating acoustic phonons that are emitted by the mw-heated 2DEG. The exciton PL quenching is associated with an exciton drag by the phonon flux towards the opposite HJ interface where the excitons recombine nonradiatively. The rate of phonon emission is determined by the 2DEG state, and thus the exciton PL responds to the changes of the 2DEG parameters.