Charged impurity scattering in two-dimensional materials with ring-shaped valence bands: GaS, GaSe, InS, and InSe

TL;DR

This paper investigates how ring-shaped valence bands in certain 2D materials influence charged impurity scattering and mobility, highlighting the dominant role of wavevector-dependent screening and impurity placement.

Contribution

It provides a detailed analysis of charged impurity scattering in 2D materials with Mexican hat valence bands, emphasizing the impact of wavevector-dependent screening and impurity location.

Findings

Wavevector dependence of screening dominates scattering trends.

Moving impurities closer to the channel significantly increases mobility.

Temperature dependence of mobility is affected by Coulomb potential variations.

Abstract

The singular density of states and the two Fermi wavevectors resulting from a ring-shaped or "Mexican hat" valence band give rise to unique trends in the charged impurity scattering rates and charged impurity limited mobilities. Ring shaped valence bands are common features of many monolayer and few-layer two-dimensional materials including the III-VI materials GaS, GaSe, InS, and InSe. The wavevector dependence of the screening, calculated within the random phase approximation, is so strong that it is the dominant factor determining the overall trends of the scattering rates and mobilities with respect to temperature and hole density. Charged impurities placed on the substrate and in the 2D channel are considered. The different wavevector dependencies of the bare Coulomb potentials alter the temperature dependence of the mobilities. Moving the charged impurities 5 $\AA$ from the center of the channel to the substrate increases the mobility by an order of magnitude.