Effects of metallic gates on AC quantum Hall measurements

Using a sample with back-gates, a linear frequency dependence of the AC quantum Hall resistance was observed on the plateau i=2 for frequencies ranging from 800 Hz to 5 kHz. The frequency coefficient, and the current dependence of R/sub H/ which depend on potentials applied to the back-gates, can simultaneously be reduced to zero. More interestingly, it is also shown that, by removing these back-gates, the losses are considerably reduced giving a negligible frequency coefficient on the order of (0.006/spl plusmn/0.030) (/spl mu//spl Omega///spl Omega/)/kHz.