Tailoring Superconducting Phases Observed in Hyperdoped Si:Ga for Cryogenic Circuit Applications

TL;DR

This study investigates superconductivity in hyperdoped silicon with gallium, focusing on how Ga cluster distribution affects low-temperature robustness and proposing conditions to enhance superconducting coherence for cryogenic applications.

Contribution

It identifies how Ga cluster distribution influences superconductivity in Si:Ga and demonstrates methods to improve coherence at millikelvin temperatures.

Findings

Reentrant resistive transition depends on Ga cluster distribution.

Optimized implantation conditions eliminate reentrant transition at 20 mK.

Enhanced superconducting coherence suitable for cryogenic circuits.

Abstract

Hyperdoping with gallium (Ga) has been established as a route to observe superconductivity in silicon (Si). The relatively large critical temperatures (T$_{\rm c}$) and magnetic fields (B$_{\rm c}$) make this phase attractive for cryogenic circuit applications, particularly for scalable hybrid superconductor--semiconductor platforms. However, the robustness of Si:Ga superconductivity at millikelvin temperatures is yet to be evaluated. Here, we report the presence of a reentrant resistive transition below T$_{\rm c}$ for Si:Ga whose strength strongly depends on the distribution of the Ga clusters that precipitate in the implanted Si after annealing. By monitoring the reentrant resistance over a wide parameter space of implantation energies and fluences, we determine conditions that significantly improve the coherent coupling of Ga clusters, therefore, eliminating the reentrant transition even at temperatures as low as 20~mK.