Tuning supercurrent in Josephson field effect transistors using h-BN dielectric: Part 2, Characterization

Josephson junction field effect transistors (JJ-FET) based on semiconductor weak-links can provide voltage-controlled supercurrent. Conventionally high-K dielectrics such as AlO_x are used on FETs or JJ-FETS, here we introduce h-BN as an alternative gate dielectric for epitaxial Al/InAs JJ-FETs. This could solve several niche difficulties: 1. Reducing surface chemistry and defect formation. 2. Prevents microwave absorption. 3. Find use as a tunnel barrier. We investigate the Josephson properties of JJ-FETs fabricated with thin h-BN flakes (5 nm - 10 nm) and show high transparency of JJ-FET from epitaxial contacts are preserved. We also find that the product of normal resistance, Rn and critical current, Ic, is comparable for devices with hBN and AlO_x dielectrics. However we observe differences in normal resistance of the junctions that suggest surface chemistry has not been affected by hBN compared to AlO_x.