Experiments on scaling in AlxGa1-xAs/GaAs heterostructures under quantum Hall conditions

The influence of repulsive (Be) and attractive (Si) scattering centers on the temperature-dependent half-width of the Shubnikovde Haas peaks B(T) and the maximum of the slope of the Hall resistance xy/B has been investigated at millikelvin temperatures for the two-dimensional electron gas in AlxGa1-xAs/GaAs heterostructures. Both sheet-doped and homogeneously doped samples were studied. In contrast to results reported for InxGa1-xAs/InP heterostructures, where a scaling exponent =0.42±0.04 with BT and (xy/B)maxT- is found and suggested to be universal, our data lead to scaling exponents that systematically increase with decreasing mobility. The transition between the integer filling factor 1 and the fractional filling factor 2/3 has been studied and a scaling behavior observed.