Orbital and valley state spectra of a few-electron silicon quantum dot

TL;DR

This study investigates the energy spectra of a few-electron silicon quantum dot, revealing how orbital and valley states evolve with electron number, which is vital for developing silicon-based spin qubits.

Contribution

It provides detailed measurements of orbital and valley state spectra in silicon quantum dots, demonstrating consistent valley splitting across different electron occupancies.

Findings

Orbital excited state energy decreases with increasing electron number.

Valley splitting remains approximately constant at ~230 μeV.

Favorable conditions for qubit operation are confirmed in the few-electron regime.

Abstract

Understanding interactions between orbital and valley quantum states in silicon nanodevices is crucial in assessing the prospects of spin-based qubits. We study the energy spectra of a few-electron silicon metal-oxide-semiconductor quantum dot using dynamic charge sensing and pulsed-voltage spectroscopy. The occupancy of the quantum dot is probed down to the single-electron level using a nearby single-electron transistor as a charge sensor. The energy of the first orbital excited state is found to decrease rapidly as the electron occupancy increases from N=1 to 4. By monitoring the sequential spin filling of the dot we extract a valley splitting of ~230 {\mu}eV, irrespective of electron number. This indicates that favorable conditions for qubit operation are in place in the few-electron regime.