The effect of external electric fields on silicon with superconducting gallium nano-precipitates

TL;DR

This study investigates superconductivity in silicon doped with gallium nano-precipitates, finding it is unaffected by high electric fields and highlighting inhomogeneities that impact its properties for nanoelectronic applications.

Contribution

It provides new experimental data on the reproducibility and electric field insensitivity of superconductivity in gallium-implanted silicon, with detailed microscopy analysis.

Findings

Superconductivity is not gateable at electric fields up to 8 MV/cm.

Presence of gallium precipitates correlates with superconductivity.

Inhomogeneities are observed, affecting superconducting properties.

Abstract

Motivated by potential transformative applications of nanoelectronic circuits that incorporate superconducting elements, and by the advantages of integrating these elements in a silicon materials platform, we investigate the properties of the superconductivity of silicon ion-implanted with gallium. Here we measure 40 different samples and explore both a variety of preparation methods (yielding both superconducting and non-superconducting samples), and the reproducibility of one of the preparation methods yielding superconducting samples. While we find agreement with the existing literature that superconducting effects are visible in this system, we also find that this superconductivity is not influenced by voltages applied to a top gate. The superconductivity in this materials system is not gateable for applied electric fields as large as 8 MV/cm. We also present results of scanning transmission electron microscopy imaging of some of the same samples for which we report electronic characterization. In agreement with the existing literature, we find that the presence of Ga precipitates is essential to the presence of a superconducting transition in these samples. However, we also find evidence for large inhomogeneities in this system, which we discuss in connection with the lack of gateability we report here.