Tuning Supercurrent in Josephson Field-Effect Transistors Using h-BN Dielectric

Area of Science:

• Materials Science
• Condensed Matter Physics
• Quantum Computing

Background:

• Epitaxial Al-InAs heterostructures are promising for mesoscopic and topological superconductivity.
• Josephson junction field-effect transistors (JJ-FETs) allow supercurrent tuning via metallic gates.

Purpose of the Study:

• To fabricate and measure gate-tunable Al-InAs JJ-FETs using hexagonal boron nitride (h-BN) as a gate dielectric.
• To investigate the compatibility of layered material transfer with Al-InAs heterostructures.
• To assess the impact of h-BN dielectric on Josephson junction properties and channel density.

Main Methods:

• Fabrication of Al-InAs JJ-FETs utilizing mechanically exfoliated and dry-transferred h-BN flakes (5 nm thick) as gate dielectric.
• Characterization of gate-tunability of supercurrent.
• Measurement of Josephson junction properties, including the product of normal resistance and critical current (IcRn).
• Complementary measurements comparing h-BN with Al2O3 dielectric for channel density changes.

Main Results:

• Achieved full gate-tunability of supercurrent in Al-InAs JJ-FETs using thin h-BN flakes.
• Preserved pristine properties of epitaxial Josephson junctions, indicated by consistent IcRn values.
• Demonstrated that h-BN dielectric results in less channel density change compared to Al2O3.

Conclusions:

• Mechanically exfoliated h-BN is a viable gate dielectric for fabricating high-quality, gate-tunable Al-InAs JJ-FETs.
• The developed fabrication process is compatible with layered material transfer and Al-InAs heterostructures.
• h-BN offers advantages over Al2O3 for preserving channel properties in JJ-FETs, advancing research in topological superconductivity.