Investigating random discrete dopant-induced variability in cryogenic gate-all-around nanosheet FETs: A quantum transport simulation study

Abstract

This study investigates the variability induced by random discrete dopants (RDDs) in the source and drain extension (SDE) regions in cryogenic $n$-type gate-all-around nanosheet field-effect transistors using the extensive quantum transport simulations. RDDs in the SDE regions effectively alter the channel length, necessitating a detailed analysis of the temperature dependence of short channel effects across a range from cryogenic (77 K) to room temperature (300 K). The results clearly demonstrate that cryogenic devices are more susceptible to random dopant fluctuation (RDF), exhibiting greater variability in threshold voltage, ON-state current, and drain-induced barrier lowering compared to devices operating at 300 K, even when the intrinsic channel device is considered. These findings emphasize the importance of rigorously addressing local variability, such as RDF, alongside process-induced variability in the design and optimization of cryogenic devices and associated circuits.