Investigation of physical limit of subthreshold swing at cryogenic temperatures in dual-gate short-channel InZnO transistors

Abstract

Subthreshold swing (SS) is a critical parameter determining transistor switching and is fundamentally limited by the energy band tails at cryogenic temperatures, which is still under investigation for amorphous oxide semiconductors. In this work, we fabricate dual-gate (DG) field-effect transistors featuring an ultra-thin (3.6 nm) indium-zinc-oxide channel deposited via supercycle atomic layer deposition. Excellent electrostatic control is achieved through DG configuration, scaled high-k dielectric and channel thickness, with a small natural length of 1.8 nm. The devices exhibit an ideal SS of 60 mV/dec across channel lengths from 140 nm down to 60 nm. Systematic temperature-dependent characterization from 398 to 14 K reveals SS values approaching the Boltzmann limit with a fitted temperature sensitivity coefficient of 0.202, near the theoretical 0.199. At 14 K, the physical limit of SS ∼10 mV/dec is sustained over three decades of current.