Optically detected far-infrared cyclotron resonance of two-dimensional electrons in a single GaAs/(Al,Ga)As heterojunction

Far-infrared (FIR) cyclotron resonance of a high-mobility two-dimensional electron gas (2DEG) in a GaAs/(Al,Ga) As single heterojunction is detected by resonant modulation of the photoluminescence. This optically detected cyclotron resonance (ODCR) of the 2DEG occurs in two photoluminescence (PL) bands originating from spatially separated sample regions: The exciton emission from the wide GaAs buffer layer is enhanced, while the photoluminescence of the 2D electrons with itinerant holes is suppressed when the 2D electrons resonantly absorb FIR radiation. The ODCR mechanism is attributed to the interaction of excitons with ballistically propagating acoustic phonons (phonon wind) emitted upon energy relaxation of 2D electrons heated by FIR. The interaction results in an effective long-range 2DEG-exciton repulsion that hinders dissociation of free excitons in the 2DEG vicinity. We show that the FIR ODCR lineshape is well described in the frame of the Drude model accounting for FIR reflection from the 2DEG. The significant difference between this FIR-induced ODCR and previously studied microwave-induced ODCR is discussed. DOI: 10.1103/PhysRevB.87.085316