Role of Interface Trap Charges in the Performance of Monolayer and Bilayer MoS2-based Field-Effect Transistors

Abstract

The two-dimensional MoS <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> -based field-effect transistor emerges as a promising candidate for scaling down the channel length beyond the end of silicon CMOS nanoelectronics. Although several recent experimental studies have reported the presence of interface trap charges between MoS <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> and oxide interface, their deleterious effects on MoS <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> -FET performance remain unexplored. Therefore, in this work, we investigate the digital performance of monolayer and bilayer MoS <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> -FETs in the presence of constant energy and Gaussian trap distributions. To this purpose, the trap charge description is introduced in device electrostatics using 2-D Poisson’s equation, which is self-consistently solved with non-equilibrium Green’s function (NEGF) equations for accurately capturing their effect in the semi-ballistic transport. It is found that monolayer MoS <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> -FET undergoes higher degradation in the drive current than bilayer MoS <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> -FET in both the cases of constant energy and Gaussian trap distributions. The interface trap charges possess severe limitations on the key MoS <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> -FET metrics, such as ON-current and sub-threshold slope, rather than the OFF-state current. Our studies suggest that minimizing the distributed trap at MoS <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> and oxide interface can significantly enhance the drive current, and hence, improve the speed and energy efficiency.