Direct observation of excited states in double quantum dot silicon single electron transistor

We report, in this paper, the detailed measurements obtained from the double quantum dot silicon single electron transistors. Both the drain current and the differential conductance measurements in large drain voltage regime show small conductance peaks - as many as seven. The differential conductance contour exhibits many small diamond-like features other than main Coulomb blockade diamonds. The extracted quantum energy of the dot is 2.52 meV, which is only six times smaller than the charging energy and the Monte-Carlo simulation results are qualitatively consistent with the measured results.