Van der Waals heterostructures for tunnel transistors

Layered semiconductors, such as transition metal dichalcogenides and black phosphorous, represent a new class of electronic materials exhibiting unique physical and chemical properties. Of particular interest for tunneling transistors (TFETs) is their inherently uniform thickness at the atomic scale arising from their layered structure. This property, theoretically leads to sharp band edges, which is an essential necessity for a steep TFET¹. Furthermore, owing to their vertical quantum confinement, the depletion width at the vertical heterojunctions is confined to the van der Waals (vdW) gap. Our group has recently explored the use of various 2D material heterojunctions for TFETs, including WSe2/MoS2 heterostacks². Our studies have shown strong interlayer coupling with gate controlled band-to-band tunneling in these vdW heterostructures. Other heterostacks with close to type III offsets have also been explored by our group, which deliver higher ON currents and steeper switching characteristics. These works demonstrate the feasibility of using 2D materials for TFETs. Significant progress has been made in the field over the past several years, however, further advancements in engineering the interface quality and contact resistance^{3 4 5 6 7} of vdW heterostructures are needed to explore the fundamental performance limits of 2D TFETs.