Epitaxial synthesis of ultrathin β-In2Se3/MoS2 heterostructures with high visible/near-infrared photoresponse

Van der Waals (vdWs) heterostructures, combining different two-dimensional (2D) layered materials with diverse properties, have been demonstrated to be a very promising platform to explore new physical phenomenon and realize various potential applications in atomically thin electronic and optoelectronic devices. Here, we report the controlled growth of vertically stacked β-In2Se3/MoS2 vdWs heterostructures (despite the existence of large lattice mismatching ~29%) through a typical two-step chemical vapor deposition (CVD) method. Crystal structure of the achieved heterostructure is characterized by transmission electron microscope, where evident Moire patterns are observed, indicating well-aligned lattice orientation. Optical characterizations indicate strong photoluminescence quenching in the heterostructure region compared with pure MoS2, revealing effective interlayer charge transfer at the heterostructure interface. Electrical device is further constructed based on the achieved heterostructure, where high on/off ratio and typical rectifying behavior is demonstrated. Upon laser irradiation, the device shows excellent photosensing properties. High responsivity of 4.47 A/W and detectivity of 1.07×109 Jones are obtained under 450 nm laser illumination with a bias voltage of 1 V, which are much better than those of CVD grown heterostructures. Most significantly, the detection range can extend to near-infrared due to the relatively small bandgap nature of β-In2Se3. With 830 nm laser illumination, the device also shows distinct photoresponse with fast response speed even operating at room temperature. The high-quality β-In2Se3/MoS2 heterostructures broaden the family of 2D layered heterostructure system and should have significant potential applications in high-performance broadband photodetectors.