Metallic and insulating behaviour of the two-dimensional electron gas on   a vicinal surface of Si MOSFETs
  The resistance R of the 2DEG on the vicinal Si surface shows an unusual behaviour, which is very different from that in the (100) Si MOSFET where an unconventional metal to insulator transition has been reported. The crossover from the insulator with dR/dT<0 to the metal with dR/dT>0 occurs at a low resistance of R_{\Box}^c \sim 0.04h/e^2. At the low-temperature transition, which we attribute to the existence of a narrow impurity band at the interface, a distinct hysteresis in the resistance is detected. At higher temperatures, another change in the sign of dR/dT is seen and related to the crossover from the degenerate to non-degenerate 2DEG. 
S. S. Safonov, S. H. Roshko, A. K. Savchenko, A. G. Pogosov, and Z. D.   Kvon