The frequency dependence of the diagonal conductivity of a 2DEG in GaAs heterostructure in the quantum Hall regime

Abstract

We have measured directly the diagonal conductivity of a 2DEG in GaAs/ A1GaAs heterostructure via a capacitively coupled structure with d.c. bias at magnetic fields up to 6 tesla. From the ungated region of a sample of Corbino geometry, the diagonal conductivity at the Landau gap regions was measured via capacitive coupling to a non-quantized 2DEG in the source and drain capacitors. A strong frequency dependence was observed over a range of frequencies from 100 Hz to 20 kHz at the temperature of 1.3 K. The result is compared to the calculations from the percolation theory. From the measurements of two different temperatures, 1.3 and 4.2 K, the activation energy for the conductivity was estimated to be about 10% of Landau level spacing.