Charge Sensing in a High-Mobility Metal-Oxide-Silicon Dual Quantum Dot Device

Spins confined in metal-oxide-silicon (MOS) heterostructures are promising qubits, demonstrating long coherence times and a large valley splitting. One of the key challenges in fabricating MOS quantum devices is to maintain a high-quality Si/SiO₂ interface without introducing shallow electron traps during high-energy processes like electron-beam lithography. In previous work we have developed a fabrication process yielding record-high mobility thin-oxide (30 nm) MOS transistors (23,000 cm²/Vs) with very low shallow defect densities and percolation thresholds (8×10¹⁰ cm^-2). In addition, we have shown that we can maintain a high-quality Si/SiO₂ interface even after irradiating these samples with an electron-beam lithography dose. Leveraging this fabrication process, we have fabricated a MOS dual quantum dot device similar to the “dual-rail” structures pioneered in Si/SiGe, featuring two parallel conduction channels defined by three overlapping layers of poly-silicon and aluminum gates. We present preliminary characterization of this device with DC transport measurements at 300 mK. Biasing one of the quantum dots into a charge sensor, we demonstrate the tunability of our device down to the few electron regime.