Single-electron charging in doped silicon double dots

We have fabricated and characterized a uniformly n-doped silicon double-dot structure. The electrical behaviour could be changed between that of a multiple tunnel junction and that of a double dot by applying appropriate gate voltages. The double-dot characteristics observed can be attributed to the geometry of the structure, and it is shown that the influence of the multiple tunnel junctions can be entirely eliminated. In the double-dot regime, characteristic charging diagrams were obtained by independently sweeping two sidegate voltages. Using a classical capacitance equivalent circuit the hexagonal lattice of the conductance resonances in the charging diagram was modelled and single-electron charging in the geometrical double dot is concluded from the match between model and experimental data.