Oscillations of 2D electron density in GaAs/Ga0.67Al0.33As heterostructures in the QHE regime

Cyclotron resonance (CR) and quantum transport measurements are performed on three GaAs/Ga 0.67 Al 0.33 As heterostructures in the quantum Hall regime at T = 2 K. The relaxation time and the 2D electron density N s are determined fitting the CR transmission curves by the Drude-type model. In all samples the density N s exhibits oscillations as a function of magnetic field. The dc quantum transport is also studied on the same structures and, assuming that the Hall resistance determines the electron density at all fields, one obtains density oscillations similar to those measured by CR. This density behaviour is modelled using a reservoir hypothesis.