Cryogenic Temperature and Doping Analysis of Source-to-Drain Tunneling Current in Ultrashort-Channel Nanosheet MOSFETs

Abstract

This work analyzes the impact of doping concentration on the temperature-dependent subthreshold current and swing saturation due to direct source-to-drain tunneling (DSDT) in short-channel silicon nanosheet (SiNS) metal–oxide–semiconductor field-effect transistors (MOSFETs). Furthermore, their influence on the drain-induced barrier lowering (DIBL) effect is investigated. Special attention is paid to the importance of the Fermi level and the average tunneling energy, whose energetic positions and distance from each other in the band diagram has a significant role in the temperature-dependent saturation behavior of the subthreshold current and swing, as well as the value of DIBL. Furthermore, we model and present with device simulation the existence of two merging subthreshold swings ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit {S}_ {\text {sth}}$ </tex-math></inline-formula> ) and DIBL effects with increasing gate bias at cryogenic temperatures. The merging is achieved by the superposition of the DSDT and thermionic emission (TE) current, which originate from their own dominated and visibly separated gate-bias regions.