Josephson Field Effect Transistors with InAs on Insulator and High Permittivity Gate Dielectrics

Abstract

InAs on Insulator (InAsOI) has been recently demonstrated as a promising platform to develop hybrid semiconducting-superconducting Josephson Junctions (JJs) and Josephson Field Effect Transistors (JoFETs). The InAsOI consists of an InAs epilayer grown onto a cryogenic-electrically-insulating InAlAs metamorphic buffer, which allows the electrical decoupling of surface-exposed adjacent devices together with a high critical current density integration. The miniaturization of Si microchips has progressed significantly due to the integration of high permittivity (high-k) gate insulators, allowing an increased gate coupling with the transistor channel with consequent reduced gate operating voltages and leakages. As well as for Si-based FETs, integrating high-k gate insulators with JoFETs promises similar advantages in superconducting electronics. Here, we investigate the gate-tunable electrical properties of InAsOI-based JoFETs featuring different high-k gate insulators, namely, HfO2 and Al2O3. We found that both the ungated and gate-tunable electrical properties of the JoFETs are strongly dependent on the insulator chosen. With both dielectrics, the JoFETs can entirely suppress the switching current and increase the normal state resistance by 10-20 times using negative gate voltages. The HfO2-JoFETs exhibit improved gate-tunable electrical performance compared to those achieved with Al2O3-JoFETs, which is related to the higher permittivity of the insulator. Gate-dependent electrical properties of InAsOI-based JoFETs were evaluated in the temperature range from 50 mK to 1 K. Moreover, under the influence of an out-of-plane magnetic field, JoFETs exhibited an unconventional Fraunhofer diffraction pattern, from which an edge-peaked supercurrent density distribution was calculated.