28 FDSOI RF Figures of Merit down to 4.2 K

This work presents a detailed RF characterization of 28 FDSOI nMOSFETs at cryogenic temperatures down to 4.2 K. Two main RF Figures of Merit (FoMs), i.e. current gain cutoff frequency (f
_T
) and maximum oscillation frequency (f
_max
), as well as parasitic elements of the small-signal equivalent circuit are extracted from the measured S-parameters. The observed behavior of RF FoMs versus temperature is discussed in terms of small-signal equivalent circuit elements, both intrinsic and extrinsic (parasitics). This study suggests 28 FDSOI nMOSFETs as a good candidate for future cryogenic applications down to 4.2 K and clarifies the origin and limitations of the performance.