Mobility anisotropy of two-dimensional semiconductors

TL;DR

This paper provides a theoretical analysis of carrier mobility anisotropy in 2D semiconductors, highlighting the dominant role of effective mass and correcting previous overestimations of anisotropic ratios.

Contribution

It derives an analytic formula for intrinsic anisotropic mobility considering LA phonon scattering, emphasizing the impact of effective mass over deformation potential and elastic modulus.

Findings

Effective mass significantly influences mobility anisotropy.

Previous estimates of anisotropic ratios were overestimated.

The study provides mobility parameters for various 2D materials.

Abstract

The carrier mobility of anisotropic two-dimensional (2D) semiconductors under longitudinal acoustic (LA) phonon scattering was theoretically studied with the deformation potential theory. Based on Boltzmann equation with relaxation time approximation, an analytic formula of intrinsic anisotropic mobility was deduced, which shows that the influence of effective mass to the mobility anisotropy is larger than that of deformation potential constant and elastic modulus. Parameters were collected for various anisotropic 2D materials (black phosphorus, Hittorf's phosphorus, BC$_2$N, MXene, TiS$_3$, GeCH$_3$) to calculate their mobility anisotropy. It was revealed that the anisotropic ratio was overestimated in the past.