Hybrid Ta-InAs nanowires for Quantum devices

The quest for Majorana zero modes and gate-tunable qubits has intensified research into novel superconductor-semiconductor hybrid nanowire systems, prompting exploration of diverse material combinations and fabrication methods. Tantalum (Ta), a type 1 superconductor, has two crystalline phases, out of which the alpha phase has a higher critical temperature (T_c) of 4.4K while beta-phase exhibits T_c less than 1K. It also has a higher superconducting gap, making it an interesting candidate in these devices against the conventionally used aluminum. In this work, we present our observations on proximity induced superconductivity in InAs nanowires coated with Ta shell. Prior to Ta deposition, the InAs surface is cleaned using atomic hydrogen to ensure transparent interface. In the case of Ta based nanowire Josephson junctions, the nanowires are first grown inclined via vapor-liquid-solid mechanism and when the wires cross, the Ta shells deposited by in-situ shadowing form an etch-free junction. In TEM, we observed the Ta to be amorphous and we measured switching currents of approximately 2μA on shell devices and ~70nA on Josephson junction devices.