EFFECT OF LONG-RANGE POTENTIAL FLUCTUATIONS ON SCALING IN THE INTEGER QUANTUM HALL-EFFECT

We report a set of transport data taken in two low-mobility GaAs/AlxGa1-xAs heterostructures. When T > 200 mK, we find that the T dependence of (d-rho(xy)/dB)max behaves differently in different Landau levels, whereas when T < 200 mK, it behaves like T-0.42 as reported by Wei et al. [Phys. Rev. Lett. 61, 1294 (1988)]. The characteristic T(= 200 mK) for observing the critical behavior is much lower than that of previous observations in the InxGa1-xAs/InP heterostructure. This lowering of T for scaling is attributed to the dominance of long-range potential fluctuations due to the remote ionized impurities in the AlxGa1-xAs.