Multifunctional Phototransistor Based on Double Van der Waals Heterojunction with Reversed Band Edge Bending

Abstract Double van der Waals heterojunctions (vdWHs) based on 2D materials showcase multifunctional properties, including anti‐ambipolar behavior and polarization‐sensitive photodetection capabilities, providing a new degree of freedom for the development of next‐generation integrated electronics and optoelectronics. Herein, this work reports an anti‐ambipolar transistor with high polarized photosensitivity based on MoS 2 /Ta 2 NiS 5 /WSe 2 double vdWH with back‐to‐back type‐I band alignment. It demonstrates a noticeable negative differential transconductance with an ultrahigh peak‐to‐valley ratio of 4.3 × 10 4 and a bidirectional transconductance variation from 41.6 to −17.5 nS when V D = 2 V. It is ascribed to the effective gate‐modulation of the reversed band edge bending at the double vdWH interfaces. Additionally, the structure benefits from a photogating effect and the anisotropic Ta 2 NiS 5 interlayer, achieving a peak responsivity of 120.58 A W −1 and a decent specific detectivity of 2.65 × 10 12 Jones at V D = 2 V and V g = 5 V and exhibiting an exceptional photocurrent anisotropic ratio of 15.31 via the photovoltaic effect under 635 nm light. These findings not only expand the potential applications of the advanced 2D Ta 2 NiS 5 material but also offer valuable insights for the development of multifunctional optoelectronic devices leveraging 2D double vdWHs.