Intrinsic Transport Properties of Electrons and Holes in Monolayer Transition Metal Dichalcogenides

TL;DR

This study investigates the intrinsic electron and hole phonon interactions in monolayer transition metal dichalcogenides using density functional theory, revealing material-specific transport properties and potential for p-type device applications.

Contribution

It provides a detailed first-principles analysis of phonon-limited transport in monolayer MX$_2$ materials, highlighting differences and identifying WS$_2$ as optimal for high mobility.

Findings

WS$_2$ exhibits the highest electron and hole mobilities.

Monolayer MX$_2$ can have hole mobilities comparable to or exceeding bulk silicon.

Acoustic phonons dominate scattering near band extrema.

Abstract

Intrinsic electron- and hole-phonon interactions are investigated in monolayer transition metal dichalcogenides MX$_2$ (M=Mo,W; X=S,Se) based on a density functional theory formalism. Due to their structural similarities, all four materials exhibit qualitatively comparable scattering characteristics with the acoustic phonons playing a dominant role near the conduction and valence band extrema at the K point. However, substantial differences are observed quantitatively leading to disparate results in the transport properties. Of the considered, WS$_2$ provides the best performance for both electrons and holes with high mobilities and saturation velocities in the full-band Monte Carlo analysis of the Boltzmann transport equation. It is also found that monolayer MX$_2$ crystals with an exception of MoSe$_2$ generally show hole mobilities comparable to or even larger than the value for bulk silicon at room temperature, suggesting a potential opportunity in p-type devices. The analysis is extended to estimate the effective deformation potential constants for a simplified treatment as well.