"Metallic" and "insulating" behavior of the two-dimensional electron gas on a vicinal surface of Si MOSFET's

The resistance R of the 2DEG on the vicinal Si surface shows unusual behavi or which is very different from that in Si(100) MOSFET's studied earlier. T he low-temperature crossover from dR/dT < 0 ("insulator") to dR/dT > 0 ("me tal") occurs at a low resistance of R-square(c) similar to 0.04 x h/e(2). T his crossover, which we attribute to the existence of a narrow impurity ban d at the inter-face, is accompanied by a distinct hysteresis in the resista nce. At higher temperatures, another change in the sign of dR/dT is seen. W e describe it by temperature dependent impurity scattering of the 2DEG near the transition from the degenerate to non degenerate state.