Design of nanodevices with low power consumption and high performance is highly desirable. Recently, a band-to-band tunneling field effect transistor (TFET) is developed, which offers an opportunity to overcome the thermal subthreshold limit. In this work, we demonstrate that two-dimensional (2D) main-group metal chalcogenides possess small effective masses and suitable band edge positions, which show potentials for TEFT devices. Then, we take GeS/SnS2-1T and GaTe-2H/SnSe2-1T van der Waals (vdW) heterostructures as examples and investigate their electronic properties under various electric fields. We find that these vdW heterostructures composed of main-group metal chalcogenides can transfer from type-II to type-III band alignment if a positive electric field is applied. In addition, the systems show a negative differential resistance (NDR) effect, which could be further enhanced if we lift the gate voltage. The simulated charge currents could be up to the order of μA, making them promising candidates for future TFET devices. Thus, our work provides a useful guideline for the design of 2D nanodevices for tunneling applications.

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