Parallel spin filling and energy spectroscopy in few-electron Si metal-on-semiconductor-based quantum dots

We report the spin filling pattern in the few electron limit of silicon metal-on-semiconductor based quantum dots (QDs). Magnetic field dependence of Coulomb oscillation peaks showed filling of parallel spins for the last few electrons. This implies the existence of a large spin exchange energy compared with the orbital level spacing, which has been predicted for relatively large silicon QDs. Our excited-state spectroscopy study confirmed a large spin exchange energy, as well as a large valley splitting at zero magnetic field.