Edge-states at the onset of a silicon trigate nanowire FET

We investigate the onset of the few-electron regime through the undoped channel of a silicon “trigate” nanowire FET [1]. Low-temperature conductance measurements together with self-consistent calculations reveal the formation of one-dimensional conduction modes localized at the two upper edges of the channel. This localization occurs from charge traps located in the gate dielectric, resulting in about 10 nm-long quantum dots. We observe single-electron tunneling across two parallel dots one in each channel edge. We find addition energies of a few tens of meV and level spacings of the order of 1meV, which we ascribe to the valley orbit splitting. Lifting the valley degeneracy leaves only a two-fold spin degenerate level, making edge quantum dots potentially promising candidates for silicon spin qubits.