The electrical characterisation of classical and quantum devices is a critical step in the development cycle of heterogeneous material stacks for semiconductor spin qubits. In the case of silicon, properties such as disorder and energy separation of conduction band valleys are commonly investigated individually upon modifications in selected parameters of the material stack. However, this reductionist approach fails to consider the interdependence between different structural and electronic properties at the danger of optimising one metric at the expense of the others. Here, we achieve a significant improvement in both disorder and valley splitting by taking a co-design approach to the material stack. We demonstrate isotopically-purified, strained quantum wells with high mobility of 3.14(8)×105 cm2/Vs and low percolation density of 6.9(1)×1010 cm−2. These low disorder quantum wells support quantum dots with low charge noise of 0.9(3) μeV/Hz1/2 and large mean valley splitting energy of 0.24(7) meV, measured in qubit devices. By striking the delicate balance between disorder, charge noise, and valley splitting, these findings provide a benchmark for silicon as a host semiconductor for quantum dot qubits. We foresee the application of these heterostructures in larger, high-performance quantum processors.
@article{arxiv.2309.02832,
title = {Low disorder and high valley splitting in silicon},
author = {Davide Degli Esposti and Lucas E. A. Stehouwer and Önder Gül and Nodar Samkharadze and Corentin Déprez and Marcel Meyer and Ilja N. Meijer and Larysa Tryputen and Saurabh Karwal and Marc Botifoll and Jordi Arbiol and Sergey V. Amitonov and Lieven M. K. Vandersypen and Amir Sammak and Menno Veldhorst and Giordano Scappucci},
journal= {arXiv preprint arXiv:2309.02832},
year = {2024}
}