Impact of Electrical Contacts on Transition Metal Dichalcogenides-Based Acoustoelectric and Acousto-Photoelectric Devices

TL;DR

This study investigates how electrical contact barriers influence the performance of WSe2-based acoustoelectric devices, revealing how contact properties and acoustic wavelength affect charge transport and photocurrent enhancement.

Contribution

It introduces combined spectroscopic techniques to analyze contact barriers and demonstrates the impact of acoustic wavelength on charge carrier dynamics in 2D material devices.

Findings

Ten-fold increase in photocurrent with acoustic wave

Spatial current redistribution depends on contact properties

Charge transport mode varies with channel length relative to acoustic wavelength

Abstract

We study the impact of electrical contact barriers in hybrid WSe$_2$-LiNbO$_3$-based acoustoelectric and acousto-photoelectric devices using a combination of scanning photocurrent and acousto-electric current spectroscopy. Static scanning photocurrent measurements provide a qualitative measure of the band-bending and spatial distribution of the Schottky barrier between semiconducting WSe$_2$ and gold electrodes whereas the surface acoustic wave-induced acousto-electric current reveals the height of the tunnelling barrier created by the van der Waals gap between the multilayered WSe$_2$ flake and the gold electrodes in addition to the Schottky barrier. The combination of both techniques shows a ten-fold increase in the photocurrent by the acoustic wave. Moreover, the observed spatial redistribution of the current is attributed to the interplay between the contact properties at the source and drain electrodes and the charge carrier dynamics induced by the surface acoustic wave. The ratio of acoustic wavelength to the electrical channel length is found to impact the SAW-induced charge carrier transport. For a channel length shorter than one acoustic wavelength, carriers undergo a seesaw-like motion which changes to charge conveyance for channel lengths comparable or exceeding the acoustic wavelength.