Quantifying Strain and Its Effect on Charge Transport in Ge/Si Core/Shell Nanowires

Area of Science:

• Semiconductor Nanostructures
• Quantum Technologies
• Materials Science

Background:

• Strain engineering is crucial for optimizing semiconductor nanostructures for quantum applications.
• Germanium/Silicon core/shell nanowires (Ge/Si CS NWs) are promising platforms for spin qubits.
• Controlling strain distribution within these nanowires is key to enhancing their performance.

Purpose of the Study:

• To investigate the relationship between core and shell thicknesses and strain distribution in Ge/Si CS NWs.
• To understand how geometry influences strain for optimizing spin qubit host properties.
• To provide design guidelines for scalable quantum device architectures.

Main Methods:

• Synthesis of Ge/Si CS NWs using Au-catalyzed chemical vapor deposition.
• Characterization via High-Resolution Transmission Electron Microscopy (HRTEM) and elemental mapping.
• Strain analysis using Geometric Phase Analysis (GPA), Raman spectroscopy, and polarization-resolved µ-Raman measurements.
• Evaluation of electronic transport properties through hole mobility measurements.

Main Results:

• Controlled synthesis of Ge/Si CS NWs with tunable dimensions.
• Quantitative analysis of strain variations based on core and shell thicknesses.
• Measurement of phonon mode splitting correlated with strain in the Ge core.
• Achieved a record high hole mobility of 25,400 cm² V⁻¹ s⁻¹.

Conclusions:

• Geometric parameters critically influence strain tuning in Ge/Si CS NWs.
• Optimized Ge/Si CS NW structures demonstrate significant potential for high-fidelity spin qubits.
• Findings offer valuable design insights for scalable quantum computing architectures.