Tunneling Diode Based on WSe₂ /SnS₂ Heterostructure Incorporating High Detectivity and Responsivity

van der Waals (vdW) heterostructures based on atomically thin 2D materials have led to a new era in next-generation optoelectronics due to their tailored energy band alignments and ultrathin morphological features, especially in photodetectors. However, these photodetectors often show an inevitable compromise between photodetectivity and photoresponsivity with one high and the other low. Herein, a highly sensitive WSe₂ /SnS₂ photodiode is constructed on BN thin film by exfoliating each material and manually stacking them. The WSe₂ /SnS₂ vdW heterostructure shows ultralow dark currents resulting from the depletion region at the junction and high direct tunneling current when illuminated, which is confirmed by the energy band structures and electrical characteristics fitted with direct tunneling. Thus, the distinctive WSe₂ /SnS₂ vdW heterostructure exhibits both ultrahigh photodetectivity of 1.29 × 10¹³ Jones (I_ph /I_dark ratio of ≈10⁶ ) and photoresponsivity of 244 A W^-1 at a reverse bias under the illumination of 550 nm light (3.77 mW cm^-2 ).