Band alignment of two-dimensional lateral heterostructures

TL;DR

This paper demonstrates that lateral 2D heterostructures have stable band alignments independent of interfacial conditions, unlike 3D heterostructures, which is crucial for designing reliable 2D electronic devices.

Contribution

It reveals that lateral 2D heterostructures inherently reach band alignment limits due to vanishing interfacial dipole effects, providing fundamental insights for device engineering.

Findings

Lateral 2D heterostructures have band alignments at Schottky-Mott and Anderson limits.

The junction width in 2D heterostructures can be an order of magnitude longer than in 3D.

First-principles calculations often misrepresent the convergence of band alignment due to slow dipole decay.

Abstract

Recent experimental synthesis of two-dimensional (2D) heterostructures opens a door to new opportunities in tailoring the electronic properties for novel 2D devices. Here, we show that a wide range of lateral 2D heterostructures could have a prominent advantage over the traditional three-dimensional (3D) heterostructures, because their band alignments are insensitive to the interfacial conditions. They should be at the Schottky-Mott limits for semiconductor-metal junctions and at the Anderson limits for semiconductor junctions, respectively. This fundamental difference from the 3D heterostructures is rooted in the fact that, in the asymptotic limit of large distance, the effect of the interfacial dipole vanishes for 2D systems. Due to the slow decay of the dipole field and the dependence on the vacuum thickness, however, studies based on first-principles calculations often failed to reach such a conclusion. Taking graphene/hexagonal-BN and MoS2/WS2 lateral heterostructures as the respective prototypes, we show that the converged junction width can be order of magnitude longer than that for 3D junctions. The present results provide vital guidance to high-quality transport devices wherever a lateral 2D heterostructure is involved.