Transition metal dichalcogenides (TMDCs) are promising candidates for future optoelectronic devices accounting for their high carrier mobility and excellent quantum efficiency. However, the limited light absorption efficiency in atomically thin layers significantly hinders photocarrier generation, thereby impairing the optoelectronic performance and hindering practical applications. Herein, we successfully synthesized In₂Se₃/WSe₂ heterostructures through a typical two-step chemical vapor deposition (CVD) method. The In₂Se₃ nanosheet with strong light absorption capability, serving as the light absorption layer, was integrated with the monolayer WSe₂, enhancing the photosensitivity of WSe₂ significantly. Upon laser irradiation with a wavelength of 520 nm, the In₂Se₃/WSe₂ heterostructure device shows an ultrahigh photoresponsivity with a value as high as 2333.5 A/W and a remarkable detectivity reaching up to 6.7 × 10¹² Jones, which is the highest among almost the reported TMDCs-based heterostructures grown via CVD even some fabricated by mechanical exfoliation (ME). Combing the advantages of CVD method such as large scale, high yield, and clean interface, the In₂Se₃/WSe₂ heterostructures would provide a novel path for future high-performance optoelectronic device.

Small contact resistance and low Schottky barrier height (SBH) are the keys to energy-efficient electronics and optoelectronics. Two-dimensional (2D) semiconductors-based field effect transistors (FETs), holding great promise for next-generation information circuits, still suffer from poor contact quality at the metal–semiconductor junction interface, which severely hinders their further applications. Here, a novel contact strategy is proposed, where Bi₂Te₃ nanosheets with high conductivity were in-situ epitaxially grown on MoS₂ as van der Waals contacts, which can effectively avoid the damage to MoS₂ caused during the device manufacturing process, leading to a high-performance MoS₂ FET. Moreover, the small work function difference between Bi₂Te₃ and MoS₂ (Bi₂Te₃: 4.31 eV, MoS₂: 4.37 eV, measured by Kelvin probe force microscopy (KPFM)), enables small band bending and Ohmic contact at the junction interface. Electrical characterizations indicate that the MoS₂ FET device with Bi₂Te₃ contacts possesses a high current on/off ratio (5 × 10⁷), large effective carrier mobility (90 cm²/(V·s)), and low flat-band SBH (60 meV), which is favorable as compared with MoS₂ FET with traditional Cr/Au electrodes contacts, and superior to the vast majority of the reported chemical vapor deposition (CVD) MoS₂-based FET device. The demonstration of epitaxial van der Waals Bi₂Te₃ contacts will facilitate the application of 2D MoS₂ nanosheet in next-generation low-power consumption electronics and optoelectronics.

Monolayer MoS₂ is a direct band gap semiconductor with large exciton binding energy, which is a promising candidate for the application of ultrathin optoelectronic devices. However, the optoelectronic performance of monolayer MoS₂ is seriously limited to its growth quality and carrier mobility. In this work, we report the direct vapor growth and the optoelectronic device of vertically-stacked MoS₂/MoSe₂ heterostructure, and further discuss the mechanism of improved device performance. The optical and high-resolution atomic characterizations demonstrate that the heterostructure interface is of high-quality without atomic alloying. Electrical transport measurements indicate that the heterostructure transistor exhibits a high mobility of 28.5 cm²/(V·s) and a high on/off ratio of 10⁷. The optoelectronic characterizations prove that the heterostructure device presents an enhanced photoresponsivity of 36 A/W and a remarkable detectivity of 4.8 × 10¹¹ Jones, which benefited from the interface induced built-in electric field and carrier dependent Coulomb screening effect. This work demonstrates that the construction of two-dimensional (2D) semiconductor heterostructures plays a significant role in modifying the optoelectronic device properties of 2D materials.