Electric-field tuning of the valley splitting in silicon corner dots

TL;DR

This study demonstrates that the valley splitting in silicon corner quantum dots can be linearly tuned using electric fields, with potential applications in electrically controlled silicon spin qubits.

Contribution

We experimentally show electric field control of valley splitting in silicon corner dots and support findings with detailed tight-binding simulations.

Findings

Valley splitting varies linearly with back-gate voltage.

Valley splitting ranges from 880 μeV to 610 μeV.

Simulation confirms experimental tunability considering surface and dopant effects.

Abstract

We perform an excited state spectroscopy analysis of a silicon corner dot in a nanowire field-effect transistor to assess the electric field tunability of the valley splitting. First, we demonstrate a back-gate-controlled transition between a single quantum dot and a double quantum dot in parallel that allows tuning the device in to corner dot formation. We find a linear dependence of the valley splitting on back-gate voltage, from $880~\mu \text{eV}$ to $610~\mu \text{eV}$ with a slope of $-45\pm 3~\mu \text{eV/V}$ (or equivalently a slope of $-48\pm 3~\mu \text{eV/(MV/m)}$ with respect to the effective field). The experimental results are backed up by tight-binding simulations that include the effect of surface roughness, remote charges in the gate stack and discrete dopants in the channel. Our results demonstrate a way to electrically tune the valley splitting in silicon-on-insulator-based quantum dots, a requirement to achieve all-electrical manipulation of silicon spin qubits.