Self-aligned gates for scalable silicon quantum computing

Silicon quantum dot spin qubits have great potential for application in large-scale quantum circuits as they share many similarities with conventional transistors that represent the prototypical example for scalable electronic platforms. However, for quantum dot formation and control, additional gates are required, which add to device complexity and, thus, hinder upscaling. Here, we meet this challenge by demonstrating the scalable integration of a multilayer gate stack in silicon quantum dot devices using self-alignment, which allows for ultra-small gate lengths and intrinsically perfect layer-to-layer alignment. We explore the prospects of these devices as hosts for hole spin qubits that benefit from electrically driven spin control via spin–orbit interaction. Therefore, we study hole transport through a double quantum dot and observe current rectification due to the Pauli spin blockade. The application of a small magnetic field leads to lifting of the spin blockade and reveals the presence of spin–orbit interaction. From the magnitude of a singlet-triplet anticrossing at a high magnetic field, we estimate a spin–orbit energy of ∼37μeV, which corresponds to a spin–orbit length of ∼48 nm. This work paves the way for scalable spin-based quantum circuits with fast, all-electrical qubit control.