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

TL;DR

This paper investigates how strain, controlled by core and shell dimensions, affects charge transport in Ge/Si nanowires, demonstrating record high hole mobility for quantum computing applications.

Contribution

It provides a detailed analysis of strain distribution and its impact on electronic properties in Ge/Si core/shell nanowires, offering new design insights for quantum devices.

Findings

Strain distribution varies with core and shell thicknesses.

Achieved record hole mobility of 25,500 cm²V⁻¹s⁻¹.

Strain influences phonon mode splitting and electronic behavior.

Abstract

Strain engineering in semiconductor nanostructures offers a promising route to optimize electronic and optical properties for advanced quantum technologies. This study explores the relationship between core and shell thicknesses and strain distribution in Ge/Si core/shell nanowires, targeting their application as hosts for spin qubits. Nanowires were synthesized using an Au-catalyzed chemical vapor deposition technique, achieving control over core and shell dimensions. High-resolution transmission electron microscopy and elemental mapping confirmed structural integrity, while Geometric Phase Analysis and Raman spectroscopy provided quantitative insights into strain variations driven by core and shell dimensions. Furthermore, polarization resolved $\mu$-Raman measurements allowed us to quantify the longitudinal and transverse phonon mode splitting as a function of strain in the Ge core. The strain dependent electronic properties were investigated by hole mobility measurements. Finally, we observe a record high hole mobility of 25,500 cm$^2$V$^{-1}$s$^{-1}$, underscoring the potential of these core/shell nanowire structures for the realization of high-fidelity spin qubits. Our findings highlight the critical role of geometry in strain tuning and provide valuable design guidelines for optimizing Ge/Si nanowires in scalable quantum device architectures.