The Observation of Percolation-Induced 2D Metal-Insulator Transition in a Si MOSFET

Abstract

By analyzing the temperature ($T$) and density ($n$) dependence of the measured conductivity ($\ddot{I}ƒ$) of 2D electrons in the low density ($\sim 10^{11}$cm${}^{-2}$) and temperature (0.02 - 10 K) regime of high-mobility (1.0 and 1.5 $\times 10^4$ cm${}^2$/Vs) Si MOSFETs, we establish that the putative 2D metal-insulator transition is a density-inhomogeneity driven percolation transition where the density-dependent conductivity vanishes as $\ddot{I}ƒ(n)\propto (n-n_p{)}^p$, with the exponent $p\sim 1.2$ being consistent with a percolation transition. The `metallic' behavior of $\ddot{I}ƒ(T)$ 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.

6 pages, 5 figures; extended version (accepted to Phys. Rev. B)