Observation of Distinct Superconducting Phases in Hyperdoped p-type Germanium

TL;DR

This study demonstrates the existence of two distinct superconducting phases in hyperdoped germanium, including a novel nano-crystalline 2D phase, which could impact quantum technology applications.

Contribution

It reveals the formation of a new nano-crystalline superconducting phase in hyperdoped germanium, characterized by quasi-2D properties and strong disorder, expanding understanding of superconductivity in Group IV semiconductors.

Findings

Identification of a nano-crystalline 2D superconducting phase

Observation of strong disorder signatures in the new phase

Potential for integration into superconducting quantum circuits

Abstract

Realization of superconductivity in Group IV semiconductors could have a strong impact in the direction quantum technologies will take in the future. Therefore, it is imperative to understand the nature of the superconducting phases in materials such as Silicon and Germanium. Here, we report systematic synthesis and characterization of superconducting phases in hyperdoped Germanium prepared by Gallium ion implantation beyond its solubility limits. The resulting structural and physical characteristics have been tailored by changing the implantation energy and activation annealing temperature. Surprisingly, in addition to the poly-crystalline phase with weakly-coupled superconducting Ga clusters we find a nano-crystalline phase with quasi-2D characteristics consisting of a thin Ga film constrained near top surfaces. The new phase shows signatures of strong disorder such as anomalous B${\rm c}$ temperature dependence and crossings in magentoresistance isotherms. Apart from using hyperdoped Ge as a potential test-bed for studying signatures of quantum phase transitions (e.g. quantum Griffith singularity), our results suggest the possibility of integration of hyperdoped Ge nano-crystalline phase into superconducting circuits due to its 2D nature.