Charge Transfer at the Hetero-Interface of WSe2/InSe Induces Efficient Doping to Achieve Multi-Functional Lateral Homo-Junctions

Charge transfer at the hetero-interface is at the center of van der Waals (vdWs) heterostructure devices for multi-functional applications. Compared with the extensively investigated photogenerated carrier transfer driven by the built-in electric field from the conduction or valence band offset, the charge transfer due to the Fermi level difference of the two adjacent constitutes, and its influence on the opto-/electronic performance of vdWs heterostructure devices are not clarified. Herein, by taking an example of WSe2/InSe heterostructure, it is demonstrated that the charge transfer at the hetero-interface is an efficient "doping" strategy to dramatically modulate the carrier densities of atomically thin counterparts due to the extension of "band bending" across the entire heterostructure, paving the way for the creation of lateral WSe2 p-n and n-n(+) homo-junctions with multi-functionalities, including promising rectification, photovoltaic, and photodetection abilities. Moreover, the device physics of lateral homo-junctions, including potential distribution, band diagram, and photocurrent generation mechanisms, is revealed by gate-dependent Kelvin probe force microscopy and scanning photocurrent measurements. This work not only provides a general avenue to build 2D lateral homo-junctions, but also give deeper insights into the device physics of the junctions by coupling scanning probe and scanning photocurrent techniques.