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

Abstract

Motivated by potential transformative applications of nanoelectronic circuits that incorporate superconducting elements and by the advantages of integrating these elements in a silicon material 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 material 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 for 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.

Tailoring superconducting phases observed in hyperdoped Si:Ga for cryogenic circuit applications

“…In this work, we study the influence of processing condition on the superconducting properties of hyperdoped Si:Ga prepared by Ga + implantation. We first demonstrate that the implantation energy of 80 keV, which is used in all previous studies of Si:Ga superconductivity 6,8,11 , leads to emergence of a re-entrant insulating state below T c . We then tailor the Ga distribution within the implanted region by tuning processing parameters such as implantation energy (E IMP ), dopant acti-vation temperature (T DA ) and Ga + fluence (Φ Ga ).…”

“…Such temperatures are commonly used for quantum devices in order to minimize the influence of thermal energy (∼ k B T) on the quantum twolevel systems. Given that the superconductivity in Si:Ga has been attributed to the presence of a few nm-thick Ga layer segregated near the top surface, it is possible that a re-entrant resistive phase exists below T c due to disorder and percolation induced by Si or SiO x mixing 7,8,11,12 . Therefore, it is critical to determine the superconducting characteristics for hyperdoped Si:Ga well below its critical temperature all the way down to mK range.…”

Observation of Distinct Superconducting Phases in Hyperdoped p-type Germanium

“…Realization of superconductivity by hyperdoping is believed to facilitate such integration. So far, superconductivity has been successfully documented for diamond 11,12 , Silicon [13][14][15] and Germanium 16,17 by hyperdoping with acceptors (i.e. B and Ga).…”