Prospects of Hysteresis-Free Abrupt Switching (0mV/dec) in Landau Switches

TL;DR

This paper investigates conditions for achieving hysteresis-free abrupt switching in Landau switches, emphasizing the importance of a flat energy landscape and challenging traditional thermodynamic limits.

Contribution

It provides a classification of charge-based switches based on energy landscapes and identifies key conditions for hysteresis-free abrupt switching in Landau switches.

Findings

A flat energy landscape is essential for hysteresis-free abrupt switching.

Hysteresis-free smooth switching can be achieved by stabilizing the unstable gate insulator.

The study offers insights that could simplify the design of next-generation charge-based logic switches.

Abstract

Sub-threshold swing (S) defines the sharpness of ON-OFF switching of a Field Effect Transistor (FET) with S=0 corresponding to abrupt switching characteristics. While thermodynamics dictates S to be greater than or equal to 60mV/dec for classical FETs, "Landau switches" use inherently unstable gate insulators to achieve abrupt switching. Unfortunately, S=0 switching is always achieved at the expense of an intrinsic hysteresis, making these switches unsuitable for low-power applications. The fundamental question therefore remains: Under what condition, hysteresis-free abrupt switching can be achieved in a Landau switch? In this paper, we first provide an intuitive classification of all charge based switches in terms of their energy landscapes and identify two-well energy landscape as the characteristic feature of Landau switches. We then use nanoelectromechanical field effect transistor (NEMFET) as an illustrative example of a Landau switch and conclude that a flat energy landscape is essential for hysteresis-free abrupt switching. In contrast, a hysteresis-free smooth sub-60mV/dec switching is obtained by stabilizing the unstable gate insulator in its unstable regime. Our conclusions have broad implications and may considerably simplify the design of next charge based logic switch.