Plasma-Induced Symmetric Ambipolar Transport in MoS2/WSe2 p-n Heterojunctions via Stacking-Order-Mediation

Ambipolar semiconductors based on 2D PN junctions have attracted significant attention and are driving new optoelectronic and logic circuit applications. However, their low carrier mobility and electron-hole mobility asymmetry (>101) resulting in poor signal resolution that limits its practical applications. This study demonstrates high-mobility and mobility-symmetric ambipolar transport in MoS2/WSe2 p-n heterojunctions through precise oxygen plasma-mediated interface engineering. The mild oxygen plasma treatment simultaneously passivates selenium vacancies in WSe2 and sulfur vacancies in MoS2, thereby reducing scattering centers and optimizing carrier concentrations. The elevated and balanced carrier concentrations on both sides of the junction effectively lower the tunneling barrier, facilitating efficient charge injection and enabling high-performance ambipolar conduction. Analysis of the charge transport mechanism reveals a direct tunneling mode at the heterointerface. By applying a 6 s low-power soft oxygen plasma treatment to MoS2 and a 30 s oxygen plasma to WSe2, the device exhibits a more than two orders of magnitude improvement in electrical performance, demonstrating symmetric ambipolar behavior with a hole mobility of 83 cm²·V-1·s-1 and an electron mobility of 42 cm²·V-1·s-1, respectively. This work establishes new design principles for high-performance ambipolar transistors and provides critical insights for logic optoelectronic devices.