Mobility of 2D materials from first principles in an accurate and automated framework

TL;DR

This paper introduces an accurate, automated first-principles framework for calculating transport properties of 2D materials, accounting for doping and dimensional effects without post-processing, and applies it to various materials to understand mobility factors.

Contribution

It develops a comprehensive first-principles method for 2D material transport properties, including doping effects, and demonstrates its application to multiple materials for mobility analysis.

Findings

Hole-doped phosphorene exhibits the highest mobility (~600 cm^2/Vs) at room temperature.

Electron-phonon coupling can increase with doping in transition-metal dichalcogenides.

Mobility is influenced by the number and anisotropy of electronic pockets.

Abstract

We present a first-principles approach to compute the transport properties of 2D materials in an accurate and automated framework. We use density-functional perturbation theory in the appropriate bidimensional setup with open-boundary conditions in the third direction. The materials are charged by field effect via planar counter-charges. In this approach, we obtain electron-phonon matrix elements in which dimensionality and doping effects are inherently accounted for, without the need for post-processing corrections. This treatment highlights some unexpected consequences, such as an increase of electron-phonon coupling with doping in transition-metal dichalcogenides.We use symmetries extensively and identify pockets of relevant electronic states to minimize the number of electron-phonon interactions to compute; the integrodifferential Boltzmann transport equation is then linearized and solved beyond the relaxation-time approximation. We apply the entire protocol to a set of much studied materials with diverse electronic and vibrational band structures: electron-doped MoS2, WS2, WSe2, phosphorene, arsenene, and hole-doped phosphorene. Among these, hole-doped phosphorene is found to have the highest mobility, with a room temperature value around 600 cm^2/(Vs). Last, we identify the factors that affect most phonon-limited mobilities, such as the number and the anisotropy of electron and hole pockets, to provide a broader understanding of the driving forces behind high mobilities in two-dimensional materials.