Band‐to‐Band Tunneling Heterojunction for High‐Performance Broadband Polarization‐Sensitive Photodetection via Band Alignment Engineering

Abstract Band alignment engineering represents an enabling approach in 2D van der Waals heterojunctions for fabricating high‐performance photodetectors. However, there is often a trade‐off between high responsivity and high response speed when using a single type of band alignment. Here, a broadband polarization‐sensitive Bi 2 Te 3 /GeSe heterojunction photodetector is designed and fabricated, whose band alignment transfers from type II to type III by applying a forward bias voltage, allowing for the photogenerated electrons in GeSe enter into Bi 2 Te 3 via band‐to‐band tunneling (BTBT) mechanism. Meanwhile, the photogenerated carriers can be easily separated without the influence of heterojunction interface barrier. The device exhibits a maximum responsivity of 1.62 × 10 4 A W −1 in the visible range and 1.31 × 10 3 A W −1 in the near‐infrared range. The device detects high‐frequency modulated light up to 15 kHz. In addition, the unexpected pyroelectric effect at 1550 nm in a Bi 2 Te 3 /GeSe heterojunction breaks symmetry limitations, generating high instantaneous currents that enhance responsivity. Significantly, a photocurrent polarization ratio of 2.08 is attained at near‐infrared band, demonstrating superior polarization‐sensitive detection and imaging capabilities. The work provides novel insights for the field of optoelectronics.