Impact of Electrical Contacts on Transition Metal Dichalcogenide-Based Acousto-Electric and Acousto-Photoelectric Devices

We study the impact of electrical contact barriers in hybrid WSe2-LiNbO3-based acousto-electric 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 WSe2 and gold electrodes, whereas the surface acoustic wave-induced acousto-electric current reveals the height of the tunneling barrier created by the van der Waals gap between the multilayered WSe2 flake and the gold electrodes in addition to the Schottky barrier. The combination of both techniques shows a 10-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 the 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 to or exceeding the acoustic wavelength.