Coulomb blockade and transport spectroscopy in short Si : MOSFET

We report Coulomb oscillations in short (50nm and 100 nm) and wide Silicon MOSFETs at very low temperature, when the source-drain conductance is below the quantum e(2)/h. the geometry is dual of a wire, where such oscillation s have been previously reported. Our observations show that the dominating best conducting channel is a localized state which can accomodate several e lectrons. This emphasizes that Coulomb blockade appears also at low tempera ture in a standart short and wide transistor-like geometry, without intenti onal confinement, as far as the conductance is below the quantum. Analysis of the non-linear transport permits to evaluate both the mean one electron spacing (few kelvins) and the Coulomb energy (few tens of kelvins) . At finite transport voltage the contributions of excited states are obser ved. Comparing the 50nm and 100nm series, we find that the size of the impu rity quantum dot roughly scales with the source-drain distance.