AC measurements of the residual longitudinal resistivity of different GaAs-based samples in the QHE regime between 3 Hz and 100 kHz

AC measurements of the longitudinal resistivity, /spl rho//sub xx/, of three QHE samples were made at frequencies up to 100 kHz, at 1.2 K and 4.3 K, on the i=1.2 and 4 plateaus. Preliminary results show a frequency dependence on the residual value of the minimum of /spl rho//sub xx/, /spl rho//sub xx//sup min/, but not, or very few on the width of the magnetic flux density range over which /spl rho//sub xx//sup min/ takes place. In the frequency domain around 1 kHz, the /spl rho//sub xx//sup min/ values lie within 0.4 m/spl Omega/ to 8 m/spl Omega/ at 1.2 K, depending on plateaus and samples used. It promises an expected quantization of the Hall resistance, /spl rho//sub xy/=R/sub H/(i), to be complete at a level of one part in 10/sup 8/.<>