Coulomb blockade in low-mobility nanometer size Si MOSFET's

We investigate coherent transport in Si metal-oxide-semiconductor field-effect transistors with nominal gate lengths 50-100 nm and various widths at very low temperature. Independent of the geometry, localized slates appear when G similar or equal to e(2)/h and transport is dominated by resonant tunnelling through a single quantum dot formed by an impurity potential. We find that the typical size of the relevant impurity quantum dot is comparable to the channel length and that the periodicity of the observed Coulomb blockade oscillations is roughly inversely proportional to the channel length. The spectrum of resonances and the nonlinear I-V curves allow us to measure the charging energy and the mean level energy spacing for electrons in the localized state. Furthermore, we find that in the dielectric regime the variance var(lng) of the logarithmic conductance lng is proportional to its average value [lng] consistent with one-electron scaling models.