“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 behavior which is very different from that in Si $\left(100\right)$ MOSFET's studied earlier. The low-temperature crossover from $\mathrm{dR}/\mathrm{dT}<\mathrm{}0\mathrm{}$ (“insulator”) to $\mathrm{dR}/\mathrm{dT}>\mathrm{}0\mathrm{}$ (“metal”) occurs at a low resistance of $R_{\square }^c\sim 0.04\times h/e^2$. This crossover, which we attribute to the existence of a narrow impurity band at the interface, is accompanied by a distinct hysteresis in the resistance. At higher temperatures, another change in the sign of $\mathrm{dR}/\mathrm{dT}$ is seen. We describe it by temperature dependent impurity scattering of the 2DEG near the transition from the degenerate to nondegenerate state.