Chip-Scale Graphene/IGZO Cold Source FET Array Enabling Sub-60 mV dec^-1 Super-Steep Subthreshold Swing

In this study, the first sub-60 mV dec^-1 super-steep subthreshold swing (SS) of graphene/InGaZnO (IGZO) cold-source field-effect transistor (CSFET) arrays is demonstrated. The linear density of states of the Dirac-cone-type graphene suppresses the Boltzmann thermal tail near the graphene/IGZO interface which in turn causes super-exponentially decaying electron density with increasing energy, leading to an extremely low off current and SS value. In particular, by introducing an HfO₂ high-k dielectric with a low body factor, the surface potential is effectively modulated, further reducing SS by ≈46.4 mV dec^-1. Furthermore, highly uniform sub-60 mV dec^-1 SS with a yield of ≈89.1% is achieved in the IGZO CSFET 8 × 8 array devices, with a record SS value of 23.66 mV dec^-1 compared to previously reported oxide-semiconductor transistors. The proposed IGZO CSFET device is expected to drive significant advancements in high-speed and ultralow-power electronic circuits.