Supercurrent Multiplexer Based on Al/InAs on Insulator Josephson Field Effect Transistors

Cryogenic hybrid superconducting electronics represent a promising candi- date for future electronic systems, combining advantages of superconductors, such as zero resistance, with the electrical properties tunability of traditional field-effect-actuated devices. In this thesis, we report on the multiplexing of supercurrent with InAs on Insulator (InAsOI), a new platform to develop super- conducting electronics. InAsOI resembles the Silicon-On-Insulator architecture enabling the realization of Josephson Junctions supporting high supercurrent density. Starting from this, we characterized high-k dielectrics fabricated via Atomic Layer Deposition, usually involved as gate insulators, namely, Al2O3 and HfO2. We extrapolated relative permittivity and dielectric strength at room and cryo- genic temperatures. The achieved results are involved in the fabrication of Josephson Field Effect Transistors (JoFETs) featuring Al as superconductor. We optimized the JoFET performance changing the gate insulator and morphology, obtaining a total su- percurrent suppression and a twentyfold increase of the normal-state resistance in the gate range 0-5 V. Eventually, we realized a 1-input-8-outputs superconducting demultiplexer featuring 14 HfO2-based JoFETs interconnected with Al traces on the same chip. We successfully steered the supercurrent into the chosen path by applying the desired gate setting, enabling supercurrent transport at frequencies up to 20 kHz. These achievements represent the first steps to the design and fabrication of InAsOI integrated superconducting electronics.