Statistics of the Coulomb-blockade peak spacings of a silicon quantum dot

We present an experimental study of the fluctuations of Coulomb-blockade peak positions of a quantum dot. The dot is defined by patterning the two-dimensional electron gas of a silicon metal-oxide-semiconductor field-effect transistor structure using stacked gates. This permits variation of the number of electrons on the quantum dot without significant shape distortion. The ratio of charging energy to single-particle energy is considerably larger than in comparable $\mathrm{GaAs}/{\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$ quantum dots. The statistical distribution of the conductance peak spacings in the Coulomb-blockade regime was found to be unimodal and does not follow the Wigner surmise. The fluctuations of the spacings are much larger than the typical single-particle level spacing and thus clearly contradict the expectation of constant interaction–random matrix theory.