Carrier Injection and Scattering in Atomically Thin Chalcogenides

TL;DR

This paper reviews how electrode contact quality and impurity scattering affect the electrical performance of atomically thin chalcogenides like MoS2, highlighting challenges in device efficiency due to thickness-dependent effects.

Contribution

It provides a comprehensive analysis of the intrinsic and extrinsic factors causing performance degradation in ultrathin 2D chalcogenide devices.

Findings

Schottky barrier height increases in thin channels due to quantum confinement.

Coulomb impurity scattering intensifies as channel thickness decreases.

Carrier mobility decreases with reduced channel thickness.

Abstract

Atomically thin two-dimensional chalcogenides such as MoS2 monolayers are structurally ideal channel materials for the ultimate atomic electronics. However, a heavy thickness dependence of electrical performance is shown in these ultrathin materials, and the device performance normally degrades while exhibiting a low carrier mobility as compared with corresponding bulks, constituting a main hurdle for application in electronics. In this brief review, we summarize our recent work on electrode/channel contacts and carrier scattering mechanisms to address the origins of this adverse thickness dependence. Extrinsically, the Schottky barrier height increases at the electrode/channel contact area in thin channels owing to bandgap expansion caused by quantum confinement, which hinders carrier injection and degrades device performance. Intrinsically, thin channels tend to suffer from intensified Coulomb impurity scattering, resulting from the reduced interaction distance between interfacial impurities and channel carriers. Both factors are responsible for the adverse dependence of carrier mobility on channel thickness in two-dimensional semiconductors.