Gate-Tunable Junctions within Monolayer MoS₂–WS₂ Lateral Heterostructures

Two-dimensional (2D) lateral heterostructures have shown promising device applications. Although the diodelike responses across the 2D lateral heterostructure have been widely reported, the essential electrical properties, such as the Fermi levels and the lateral built-in potential, have been barely studied, especially with the applied gate voltage. In this work, we report the highly gate-tunable junction within monolayer MoS2-WS2 lateral heterostructures synthesized by our developed shortcut growth strategy. The quantitative determination between the gate voltage and the built-in potential has been revealed by the combined use of Kelvin probe force microscopy and I-V characteristics, in good agreement with the theoretical calculation results. A built-in potential up to 262 meV is observed at V-g = 40 V, which is three times larger than that at V-g = 0 V. A trap density mediated mechanism is proposed to explain the highly gatetunable built-in potential. Based on the band-discontinuity mode, the energy-band diagram of the monolayer MoS2-WS2 lateral heterostructures is presented, which belongs to the 2D type II n-n heterojunction. Our findings demonstrate the strongly gate voltage-dependent and highly tunable built-in potential within the 2D type II heterojunction, which will become the novel building blocks for 2D optoelectronic, photodetection, and photovoltaic devices.