Dynamical screening of ionized impurities between barrier-separated two-dimensional electron gases

The authors report the observation of a dynamical screening effect of ionized impurities between two inversion layers separated by a doped 200 A barrier. They performed low temperature Shubnikov-de Haas and quantum Hall effect measurements in a GaAs-AlGaAs-GaAs double heterostructure. At low magnetic fields a density enhancement of one layer not only results in a mobility enhancement of the layer itself but also in a mobility enhancement of the other electron layer lying on the opposite side of the barrier. A fit to theoretical mobility calculations provides a conclusive illustration of this effect. At high magnetic fields this screening effect is shown by an unusual linewidth variation of the SdH oscillations due to an oscillatory polarizability and hence screening of the two-dimensional electron gases.