AC conductivity of (AlGa)AsGaAs heterostructures and silicon MOSFETS in the quantum Hall regime

We have measured the two-terminal AC conductance of (AlGa)AsGaAs heterostructures and a silicon MOSFET up to 50 MHz. While the ungated heterostructure samples show no frequency dependence in the integer and no additional structure in the fractional quantum Hall regimes, the gated silicon MOSFET shows strong frequency dependence of the two-terminal AC conductance due to coupling of the signal from the 2DEG to the gate. We have also measured the capacitance of the silicon MOSFET under the same circumstances, and thereby confirm the role of the gate in coupling the high frequency signal. © 1986.