Ultralow subthreshold swing of 9 mV/dec for planar bulk GaAs MOSFETs at 4 K in quantum computing applications

A record-low subthreshold swing (SS) of 9 mV/dec at 4 K has been achieved in planar bulk GaAs metal–oxide–semiconductor field-effect transistors (MOSFETs). The measured SS in our devices decreased with temperature, from 60 mV/dec at 300 K to 19 mV/dec at 77 K, approaching the Boltzmann limit, before saturating at 9 mV/dec at a critical temperature (Tc) of 28 K and below. This significant reduction in SS was made possible by the in situ deposition of an Al2O3/Y2O3 gate dielectric on GaAs. Despite having a thick channel and high doping in our devices, the measured SS at 4 K is lower than those of some Si MOSFETs and commercial InP high-electron-mobility transistors used in quantum computing and is comparable to the low values observed in state-of-the-art devices using ultra-thin channels and/or low doping. These experimental results underscore the potential of our planar bulk GaAs MOSFETs as a promising candidate for low-power, low-noise cryogenic electronics, particularly in quantum computing applications.