Enhancing Valley Splitting in Si/SiGe Wiggle Well Quantum Dots through Integrated Stressor–Gate Architectures

Achieving consistently high valley splitting is essential for scaling silicon quantum-dot arrays for quantum computing, where low valley splitting causes leakage and control errors. Shear strain in a Si/SiGe heterostructure hosting a wiggle well is predicted to yield deterministically large valley splitting [1]. We report simulations of the strain in Si/SiGe heterostructures from nanoscale TiN stressors deposited over electrostatic gates. Although the intervening gates reduce the strain in the quantum well, values up to 0.3% are achievable for reasonable intrinsic TiN stress. We establish engineering constraints for integrating these stressors into devices by analyzing both the electrostatic effects of strain and the mechanical response of the materials. We identify an optimal stressor size, with the induced strain decreasing for stressors that are too large or too small. Finally, we describe how strain from nanofabricated gates modifies the total strain field, examining this interplay from simplified structures to full device architectures.

1. “Coupling conduction-band valleys in SiGe heterostructures via shear strain and Ge concentration oscillations.” Benjamin D. Woods, et al., npj Quantum Inf 10, 54 (2024).