Tuning supercurrent in Josephson field effect transistors using h-BN dielectric

TL;DR

This paper demonstrates the fabrication of gate-tunable Josephson junctions using h-BN as a dielectric, showing full supercurrent control and improved surface quality compared to traditional dielectrics, advancing topological superconductivity research.

Contribution

It introduces a novel fabrication process for Al-InAs JJ-FETs with h-BN dielectric, enabling full gate tunability and reduced surface doping, outperforming conventional AlO$_{ m x}$ dielectrics.

Findings

Full supercurrent tunability with 5 nm h-BN dielectric.

Higher resistance indicating less surface doping with h-BN.

Comparable I$_{ m c}$R$_{ m n}$ product to conventional devices.

Abstract

The transparent interface in epitaxial Al-InAs heterostructures provides an excellent platform for potential advances in mesoscopic and topological superconductivity. Semiconductor-based Josephson Junction Field Effect Transistors (JJ-FETs) fabricated on these heterostructures have a metallic gate that tunes the supercurrent. Here we report the fabrication and measurement of gate-tunable Al-InAs JJ-FETs in which the gate dielectric in contact with the InAs is produced by mechanically exfoliated hexagonal boron nitride (h-BN) followed by dry transfer using a van der Waals-mediated pick up process. We discuss the fabrication process that enables compatibility between layered material transfer and Al-InAs heterostructures to avoid chemical reactions and unintentional doping that could affect the characteristics of the JJ-FET. We achieve full gate-tunablity of supercurrent by using only 5~nm thick h-BN flakes. We contrast our process with devices fabricated using a conventional AlO$_{\rm x}$ gate dielectric and show that h-BN could be an excellent competing dielectric for JJ-FET devices. We observe that the product of normal resistance and critical current, I$_{\rm c}$R$_{\rm n}$, is comparable for both types of devices, but strikingly higher R$_{\rm n}$ for the h-BN-based devices indicating that the surface is doped less compared to AlO$_{\rm x}$ gate dielectric.