Van der Waals metal-semiconductor junction: weak Fermi level pinning enables effective tuning of Schottky barrier

TL;DR

This paper demonstrates that using 2D metals in van der Waals heterojunctions with 2D semiconductors weakens Fermi level pinning, enabling effective tuning of Schottky barriers for improved electronic device performance.

Contribution

It reveals that 2D metals form weakly pinned junctions with 2D semiconductors, allowing Schottky barrier tuning, which is a significant advancement over conventional metal contacts.

Findings

Weak Fermi level pinning at vdW MSJs due to suppression of metal-induced gap states.

Schottky barriers can be effectively tuned and even eliminated using suitable 2D metals.

Potential for improved device applications with tunable Schottky barriers in 2D heterojunctions.

Abstract

Two-dimensional (2D) semiconductors have shown great promise in (opto)electronic applications. However, their developments are limited by a large Schottky barrier (SB) at the metal-semiconductor junction (MSJ), which is difficult to tune by using conventional metals due to the strong Fermi level pinning (FLP) effect. Here we show that, this problem can be overcome by using 2D metals, which are bounded with 2D semiconductors through van der Waals (vdW) interaction. This success relies on a weak FLP at the vdW MSJ, which is attributed to the suppression of metal-induced gap states. Consequently, the SB becomes tunable and can vanish with proper 2D metals (e.g. H-NbS2). This work not only offers new insights into the fundamental properties of heterojunctions, but also uncovers great potential of 2D metals in device applications.