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.