Valley splitting correlations across a silicon quantum well containing germanium

Area of Science:

• Quantum Computing
• Materials Science
• Semiconductor Physics

Background:

• Electron spin qubits in SiGe/Si/SiGe heterostructures are key for quantum computers.
• Near-degenerate electron valley states in silicon quantum wells reduce qubit fidelity.
• Valley splitting is sensitive to microscopic disorder in SiGe alloys and interfaces.

Purpose of the Study:

• Investigate valley splitting variations in a 1D quantum dot array within a SiGe/Si/SiGe heterostructure.
• Understand the impact of alloy disorder on valley splitting at different length scales.
• Inform scalable quantum device design for silicon-based quantum computers.

Main Methods:

• Fabrication of a 1D quantum dot array in a Si$_{0.972}$Ge$_{0.028}$ quantum well by Intel.
• Experimental study of valley splitting variations across the quantum dot array.
• Analysis of correlations in valley splitting at sub-100 nm and >1 μm length scales.

Main Results:

• Observed correlations in valley splitting at both single-gate (sub-100 nm) and device (>1 μm) length scales.
• Results align with theoretical predictions and simulations dominated by alloy disorder.
• Demonstrated the mesoscopic nature of valley splitting variations in Si/SiGe heterostructures.

Conclusions:

• Alloy disorder significantly influences valley splitting in SiGe quantum wells.
• Understanding these mesoscopic variations is essential for improving qubit fidelity.
• The findings provide critical insights for the scalable manufacturing of silicon quantum processors.