Two-dimensional Ta₂NiSe₅/GaSe van der Waals heterojunction for ultrasensitive visible and near-infrared dual-band photodetector

Dual-band photodetectors have attracted intensive attention because of the requirement of multiband information [such as visible (VIS) and near-infrared (NIR)] in multicolor imaging technology, in which additional information beyond human vision could assist object identification and navigations. The use of 2D materials can break the limitation of high cost of conventional epitaxial semiconductors and a complex cryogenic cooling system for multi-band detection, but there is still much room to improve the performance, especially in responsivity and signal noise ratio. Herein, we have fabricated a VIS-NIR dual-band photodetector based on a multilayer Ta₂NiSe₅/GaSe heterojunction. Benefiting from the type-II heterojunction, the separation of photo-induced carriers is naturally enhanced, which promotes the responsivity of this dual-band photodetector to 4.8 A W⁻¹ (VIS) and 0.15 A W⁻¹ (NIR) at room temperature with a suppressed dark current at ∼4 pA. Our work suggests that the Ta₂NiSe₅/GaSe heterostructure is a promising candidate for ultrasensitive VIS-NIR dual-band photodetection.