2D Double Heterostructure Infrared Photodetector with Type‐III Band Alignment by Incorporating Bi₂Se₃ Layer

Abstract

Two‐dimensional (2D) self‐powered photodetectors have attracted considerable attention due to their exceptional sensitivity, and low dark current. However, the poor responsivity of single heterojunctions with type‐III band alignment is primarily attributed to band‐to‐band tunneling. The implementation of a double heterojunction has the potential to enhance photovoltaic responsivity, enable broadband detection, and improve response speed. In this study, a back‐to‐back type‐III band alignment based on SnSe₂/Bi₂Se₃/MoTe₂ double heterostructure by dry transfer method is designed. As a result, it exhibited an impressive photovoltaic performance in the overlapping region. Achieving a maximum responsivity (R), external quantum efficiency (EQE), photoelectric conversion efficiency (PCE), and specific detectiviy (D^*) of 493 mA W⁻¹, 76 %, 3 % and 1.8 × 10¹¹ Jones at a gate voltage (V_g) of 60 V under 808 nm illumination. It can be ascribed to the effective depletion region at the SnSe₂/Bi₂Se₃ interface and the reversed band edge from depletion to accumulation mode at Bi₂Se₃/MoTe₂ interface. In addition, a faster response speed of 553/583 µs and a lower dark current of 2.9 pA can be obtained. Moreover, this double heterostructure achieves better photovoltaic performance with V_g compared to the single MoTe₂/SnSe₂ heterojunction. These results demonstrates the potential as a candidate for back‐to‐back type‐III band alignment in low power optoelectronics.