Single electron and dopant control in silicon transistors

Orateur : Soutenance de thèse de Benoit VOISIN

Recent progress in Silicon-On-Insulator transistors fabrication have concerned a dimensions reduction, up to a few tens of nanometers, and an improvement of the leads. This allows to study the few electrons regime at low temperature. These latter are confined in the cor ners of the nanowire, where the electric field is maximized. This leads for the silicon valley degeneracy to be lifted, with a singlet for the two-electron ground state at zero magnetic field. We also investigate the interactions between these confined electrons and the electrons of the contacts conduction bands, with the Kondo effect and the Fermi-edge singularity. The dopants, essential ingredients of the transistors fabrication, naturally lift the valley degeneracy thanks to their deep confinement potential. First, by tuning the transverse electric field, we investigate the influence of the complex environment on a donor’s ionization according to its position in the nanowire. We then realized the first Coupled-Atom Transistor, where the transport is controlled by the alignment of the ground states of two dopants placed in series. We could measure an energy splitting between the two first states of the order of 10 meV, one order of magnitude larger than that of the first electrons of the conduction band. This large separation allows to manipulate the electronic states in the ten’s gigahertz regime. We induce one-electron interferences between the ground states of the two dopants, opening the way towards coherent electron manipulations in dopant-based devices.

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