Characterization of a gate-defined double quantum dot in a Si/SiGe nanomembrane

Area of Science:

• Quantum Computing
• Materials Science
• Condensed Matter Physics

Background:

• Traditional silicon-germanium (Si/SiGe) quantum dots rely on strain-graded virtual substrates, introducing defects like misfit dislocations.
• These defects cause strain inhomogeneities and mosaic tilt, negatively impacting quantum device performance.
• A new approach using SiGe nanomembranes offers elastic strain relaxation, avoiding misfit dislocations.

Purpose of the Study:

• To fabricate and characterize a gate-defined double quantum dot in a Si/SiGe nanomembrane.
• To investigate the feasibility of using nanomembranes as virtual substrates for defect-free quantum dot formation.
• To demonstrate the controllability of the fabricated double quantum dot.

Main Methods:

• Fabrication of a Si/SiGe nanomembrane heterostructure using two epitaxial growth steps and a wet-transfer process.
• Formation of a gate-defined double quantum dot within the nanomembrane.
• Characterization of the double quantum dot, including tuning inter-dot coupling and identifying spin states.

Main Results:

• Successful fabrication of a gate-defined double quantum dot in a Si/SiGe nanomembrane.
• Demonstrated control over inter-dot tunnel coupling.
• Identified spin states and measured a singlet-to-triplet transition under an applied magnetic field.
• The double quantum dot functioned effectively despite a nearby buried non-epitaxial interface.

Conclusions:

• SiGe nanomembranes provide a viable, defect-free platform for creating high-quality quantum dots.
• The developed fabrication method allows for precise control over quantum dot properties.
• This work advances the development of scalable quantum computing architectures based on Si/SiGe heterostructures.