Nonbolometric mechanism of far-infrared photoresponse in quantum Hall systems

We have performed time-resolved measurements of the far-infrared photoconductivity of the two-dimensional electron system (2DES) in GaAs/AlGaAs heterostructures in the integer quantum Hall regime (near filling factor v = 2) by the application of a p-Ge laser radiation. We have found that the photoresponse (PR) signal has two components, a bolometric component with a decay time not longer than 1-2 mus, and a cyclotron resonance-related component of opposite polarity with a decay time of about 4-5 mus. We have observed a strong dependence of the PR signal on the filling factor, sample current and laser intensity. Surprisingly, we did not find a pronounced dependence of the PR decay times on these parameters and on the electron mobility, irrespective of the time constant of our setup. (C) 2002 Elsevier Science B.V. All rights reserved.