Engineering Energy Bands in 0D-2D Hybrid Photodetectors: Cu-Doped InP Quantum Dots on Type-III SnSe2/MoTe2 Heterojunction

Two-dimensional (2D) self-driven photodetectors have emerged as a compelling area of research, offering advantages such as miniaturization, weak light detection, high photosensitivity, and low noise levels. However, current type-III 2D heterojunction photodetectors often suffer from low self-driven responsivity and medium Ilight/Idark ratios. In this work, a novel device architecture that addresses these challenges is constructed by incorporating Cu-doped InP/ZnSeS/ZnS core-shell quantum dots (QDs) onto a type-III SnSe2/MoTe2 2D heterojunction. The strategically engineered energy band structure of the Cu-doped QDs facilitates carrier transport with SnSe2/MoTe2 to form back-to-back type-II and type-III band alignments. As a result, under 532 nm illumination, the hybrid device exhibits remarkable visible light self-driven performance metrics with the help of the photogating effect: an ultra-low dark current of 23 fA, with responsivity and external quantum efficiency enhanced to 459 mA W-1 and 109%, respectively, surpassing theoretical values by fourfold compared to those of pure SnSe2/MoTe2, a low noise equivalent power (NEP) of 0.87 × 10-2 pW Hz-1/2, a realistic specific detectivity of 1.45 × 1011 Jones, a large Ilight/Idark ratio of 106 and a swift response time of 1.16 ms/1.14 ms with stable operation. These results demonstrate that energy band engineering of Cu-doped QDs can significantly enhance the performance of 2D type-III heterojunctions in the visible range, laying a foundation for future gate-tunable optoelectronic devices.