Anisotropic Disorder in High Mobility 2D Heterostructures and its Correlation to Electron Transport

Surface morphology of high mobility heterostructures is examined and correlated with d.c. transport. {\it All} samples examined show evidence of lines in the [1$\bar{1}$0] direction with roughness ranging from small amplitude features to severe anisotropic ridges. Transport in these samples is consistent with that in samples having artificially induced 1D charge modulations. The native surface properties reflect a prevalent, anisotropic disorder affecting 2D electron conduction. Importantly, the native lines are orthogonal to the stripes theoretically proposed to explain high Landau level transport anisotropies.