Quantum point contact in a magnetic field: Far-infrared resonant heating observed in photoconductivity

We report on the far-infrared photoresponse of a quantum point contact devi ce fabricated on a top-gated GaAs/AlGaAs heterostructure. The top-gated arc hitecture avoids the disorder built into conventional modulation-doped stru ctures. We observe a distinctive far-infrared magnetophotoresponse. This de pends on the wavelength of the radiation and on the carrier density, which is controlled by the gate voltage. We conclude by comparison with transport data that the oscillations observed in photoconductivity and which are cen tred around the cyclotron energy arise from the resonant heating of electro ns by the far-infrared radiation. (C) 1999 American Institute of Physics. [ S0003-6951(99)03346-X].