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 (σ) of two-dimensional (2D) electrons in the low-density (∼ 1011 cm-2) and temperature (0.02-10 K) regimes of high-mobility (1.0 and 1.5× 104 cm2 /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 σ (n) (n- np) p, with the exponent p∼1.2 being consistent with a percolation transition. The "metallic" behavior of σ (T) for n> np is shown to be well described by a semiclassical Boltzmann theory, and we observe the standard weak localization-induced negative magnetoresistance behavior, as expected in a normal Fermi liquid, in the metallic phase. © 2009 The American Physical Society.