Nonmonotonic Variations of the Conductance with Electron Density in ∼70-nm-Wide Inversion Layers

The conductance of metal-oxide-silicon field-effect transistors with ∼70-nm-wide inversion layers exhibits nonmonotonic variations with electron density below 15 K. The variations are largest at low electron concentrations and are the result of variations of the activation energy $E_A$. When $E_A$ is largest the current is found to be limited by spatial barriers which contain tunneling channels at discrete energies, as in the model of Azbel.