Effect of repulsive and attractive scattering centers on the magnetotransport properties of a two-dimensional electron gas

GaAs/AlGaAs heterostructures systematically doped with additional Be or Si impurities near the two-dimensional electron gas show distinct shifts of the quantum Hall plateaus and of the minima in the longitudinal resistivity ${\mathrm{\rho }}_{\mathrm{xx}}$ relative to the expected values of the Landau-level filling factor. A quantum Hall plateau ${\mathrm{\rho }}_{\mathrm{xy}}$=h/${\mathrm{e}}^2$ which does not cross the classical straight line ${\mathrm{\rho }}_{\mathrm{xy}}^0$=B/${\mathrm{n}}_{\mathrm{s}}$e is observed. The results are explained by a microscopic transport calculation emphasizing non-Born scattering of electrons by individual impurities.