Visualization of Local Conductance in MoS2/WSe2 Heterostructure Transistors

TL;DR

This study uses microwave microscopy to visualize local conductance in MoS2/WSe2 heterostructure transistors, revealing anti-ambipolar behavior and charge distribution that elucidate the microscopic transport mechanisms in vdW heterostructures.

Contribution

It provides the first quantitative electrical imaging of MoS2/WSe2 heterostructures, linking local conductance variations to band bending and depletion regions.

Findings

Observation of anti-ambipolar transfer characteristics.

Identification of charge balance in high-current regions.

Visualization of lateral band bending and depletion zones.

Abstract

The vertical stacking of van der Waals (vdW) materials introduces a new degree of freedom to the research of two-dimensional (2D) systems. The interlayer coupling strongly influences the band structure of the heterostructures, resulting in novel properties that can be utilized for electronic and optoelectronic applications. Based on microwave microscopy studies, we report quantitative electrical imaging on gated molybdenum disulfide (MoS2)/tungsten diselenide (WSe2) heterostructure devices, which exhibit an intriguing anti-ambipolar effect in the transfer characteristics. Interestingly, in the region with significant source-drain current, electrons in the n-type MoS2 and holes in the p-type WSe2 segments are nearly balanced, whereas the heterostructure area is depleted of mobile charges. The configuration is analogous to the p-i-n diode, where the injected carriers dominate in the recombination current. The spatial evolution of local conductance can be ascribed to the lateral band bending and formation of depletion regions along the line of MoS2-heterostructure-WSe2. Our work vividly demonstrates the microscopic origin of novel transport behaviors, which is important for the vibrant field of vdW heterojunction research.