Observation of percolation-induced two-dimensional metal-insulator transition in a Si MOSFET

By analyzing the temperature (T) and density (n) dependence of the measured conductivity (sigma) of two-dimensional (2D) electrons in the low-density (similar to 10(11) cm(-2)) and temperature (0.02-10 K) regimes of high-mobility (1.0 and 1.5 x 10(4) cm(2)/Vs) Si metal-oxide-semiconductor field-effect transistors, we establish that the putative 2D metal-insulator transition is a density-inhomogeneity-driven percolation transition where the density-dependent conductivity vanishes as sigma(n)(proportional to) (n-n(p))(p), with the exponent p similar to 1.2 being consistent with a percolation transition. The metallic behavior of sigma(T) for n > n(p) is shown to be well described by a semi-classical Boltzmann theory, and we observe the standard weak localization-induced negative magnetoresistance behavior, as expected in a normal Fermi liquid, in the metallic phase.