Sub-threshold channels at the edges of nanoscale triple-gate silicon transistors

We investigate by low-temperature transport experiments the sub-threshold behavior of triple-gate silicon field-effect transistors. These three-dimensional nano-scale devices consist of a lithographically defined silicon nanowire surrounded by a gate with an active region as small as a few tens of nanometers, down to 50x60x35 nm^3. Conductance versus gate voltage show Coulomb-blockade oscillations with a large charging energy due to the formation of a small potential well below the gate. According to dependencies on device geometry and thermionic current analysis, we conclude that sub-threshold channels, a few nanometers wide, appear at the nanowire edges, hence providing an experimental evidence for the corner-effect.