Calculation of Field Dependent Mobility in MoS2 and WS2 with Multi-Valley Monte Carlo Method

Abstract

Since the two dimensional (2D) material are found to have potential for transistor application due to their suppression in short channel effect, they have attracted significant attention from worldwide researchers, and gradually demonstrate the potential for the next-generation transistors. In all of 2D materials, transition metal dichalcogenide (TMD) monolayers are the most popular ones because they have wider bandgap to provide better on/off ratio, and also have good mobility in theoretical prediction [1] . In recent years, there are some groups using TMD monolayers to make transistors and getting on/off ratio larger than 10 7 [2] . However, due to difficulties to grow perfect 2D monolayer, mobility reported by experiments is much lower than the theoretical prediction. The real intrinsic transport properties of TMD materials are still unclear. As a result, it is needed to be further discussed. There are several ways to calculate mobility. One common way is Boltzmann transport equation. Another way is Monte Carlo approach, which can simulate the movement of carriers in materials. It can calculate the velocity under different electric fields and also saturation velocity. As transistors get smaller, besides low-field mobility, high-field velocity becomes more critical. As a result, in this work, Monte Carlo method is adopted to simulate transport of electrons in monolayer MoS 2 and WS2 2 . We will discuss the electron velocity under different electric fields and also discuss the influence of satellite Q valleys on electron transport in both TMD materials.