Low disorder and high valley splitting in silicon
Davide Degli Esposti (TU Delft - QuTech Advanced Research Centre, Kavli institute of nanoscience Delft, TU Delft - QCD/Scappucci Lab)
Lucas E.A. Stehouwer (Kavli institute of nanoscience Delft, TU Delft - QuTech Advanced Research Centre, TU Delft - QCD/Scappucci Lab)
Önder Gül (TU Delft - QuTech Advanced Research Centre, TNO, TU Delft - QRD/Kouwenhoven Lab)
Nodar Samkharadze (TU Delft - BUS/TNO STAFF, TU Delft - QuTech Advanced Research Centre, TNO)
Corentin Déprez (TU Delft - QuTech Advanced Research Centre, Kavli institute of nanoscience Delft, TU Delft - QCD/Veldhorst Lab)
Marcel Meyer (TU Delft - QuTech Advanced Research Centre, TU Delft - QCD/Veldhorst Lab, Kavli institute of nanoscience Delft)
Ilja N. Meijer (Student TU Delft, Kavli institute of nanoscience Delft)
Larysa Tryputen (TU Delft - QuTech Advanced Research Centre, TU Delft - BUS/TNO STAFF, TNO)
Saurabh Karwal (TU Delft - QuTech Advanced Research Centre, TU Delft - BUS/TNO STAFF, TNO)
Lieven M.K. Vandersypen (Kavli institute of nanoscience Delft, TU Delft - QN/Vandersypen Lab, TU Delft - QuTech Advanced Research Centre)
Amir Sammak (TU Delft - QuTech Advanced Research Centre, TNO, TU Delft - BUS/TNO STAFF)
Menno Veldhorst (Kavli institute of nanoscience Delft, TU Delft - QuTech Advanced Research Centre, TU Delft - QN/Veldhorst Lab)
Giordano Scappucci (Kavli institute of nanoscience Delft, TU Delft - QuTech Advanced Research Centre, TU Delft - QCD/Scappucci Lab)
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Abstract
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 V−1 s−1 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 Hz−1/2 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.
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