Two-dimensional transition metal dichalcogenides van der Waals heterojunctions with broken-gap for tunnel field-effect transistors applications

The scaling down of transistors is nearing the limits dictated by Moore's Law, primarily due to the quantum tunneling effect. This challenge has spurred considerable interest in exploring novel materials characterized by broken-gap band alignment. Among these materials, two-dimensional (2D) materials-based van der Waals heterojunctions (vdWHs) have emerged as promising candidates, owing to their nanoscale dimensions, which render them suitable for transistor construction. Type-III vdWHs, in particular, have been investigated for their ability to facilitate rapid quantum Band-To-Band Tunneling (BTBT), thereby enabling low-power charge transport. In our study, we conducted a detailed analysis of four vdWHs comprised of HfSe2 and WXY (where X and Y represent Se or Te). Our findings indicate that 2D WSeTe (or WTe2)/HfSe2 vdWHs exhibit a broken-gap band alignment (type-III) under the influence of an external electric field, thus showcasing potential for integration into future tunnel field-effect transistors (TFETs). Additionally, our investigation revealed that the band gap of two other vdWHs, WTeSe (or WSe2)/HfSe2, varies linearly with the external electric field, fluctuating between 0.4 eV and 1.0 eV. This characteristic makes them well-suited for application as infrared detectors. By unveiling the distinct properties of these vdWH configurations, our research not only anticipates the emergence of a notable type-III band alignment vdWH but also underscores the potential of 2D vdWHs in optical sensor applications.