Photodiode-Like Behavior and Excellent Photoresponse of Vertical Si/Monolayer MoS2 Heterostructures

Abstract

Monolayer transition metal dichalcogenides (TMDs) and their van der Waals heterostructures have been experimentally and theoretically demonstrated as potential candidates for photovoltaic and optoelectronic devices due to the suitable bandgap and excellent light absorption. In this work, we report the observation of photodiode behavior in (both n-and p-type) silicon/monolayer MoS 2 vertical heterostructures. The photocurrent and photoresponsivity of heterostructures photodiodes were dependent both on the incident light wavelength and power density, and the highest photoresponsivity of 7.2 A/W was achieved in n-Si/ monolayer MoS 2 vertical heterostructures photodiodes. Compared with n-Si/MoS 2 heterostructures, the photoresponsivity of p-Si/MoS 2 heterostructure was much lower. Kelvin probe microscope (KFM) results demonstrated the more efficient separation of photogenerated excitons in n-Si/MoS 2 than that in p-Si/ MoS 2 . Coupling KFM results with band alignments of (p-, n-) Si/MoS 2 heterostructures, the origins of photodiode-like phenomena of p-Si/MoS 2 and n-Si/MoS 2 have been unveiled, that is intrinsic built-in electric field in p-n junction, and modulated barrier height and width at the interface in n-n junction. Our work may benefit to the deep understanding of the integration of two-dimensional materials with more conventional three-dimensional semiconductors, and then contribute to the developments in the area of van der Waals heterostructures.T wo-dimensional transition metal dichalcogenides (TMDs) have been experiencing significant progress because of the wide range of physical and chemical properties from the ultrathin planar structures at the atomic scale, such as strong electron-hole confinement, and excellent mechanical and thermal stability 1-4 . Besides, due to the relatively small bandgap, TMDs are also considered as excellent light absorbers, stimulating the development of TMDs-based photovoltaic and optoelectronic devices recently 5,6 . Molybdenum disulfide (MoS 2 ), a typical member of TMDs, is demonstrated as a promising candidate that goes beyond graphene for next generation of optoelectronics and spintronics due to the intrinsic and tunable bandgap, relatively high carrier mobility, and strong coupling of spin and valley degrees 7-9 . In the past few years, more researches concentrated on pursuing better photoresponsivity and broad wavelength response of MoS 2 -based photodetectors 10-14 . For example, Yin et al. first fabricated monolayer MoS 2 phototransistor with higher responsivity (7.5 mA/W) than that of graphene 10 . The wavelength-dependent photosensivity of monolayer to trilayer MoS 2 field-effect transistors was investigated by Im et al., and the results revealed that monolayer and bilayer MoS 2 exhibited excellent photodetection capabilities for green light, while tri-layer MoS 2 was efficient for red light detection 12 . By optimizing the carrier mobility, electrical contact quality and positioning technique, the maximum external photoresponsivity of 880 A/W was achieved for m...

Progress, Challenges, and Opportunities for 2D Material Based Photodetectors

“…Based on the most widely studied MoS 2 material, many hybrid structures have been fabricated, for example, with reduced graphene oxide (rGO) film, graphene quantum dots and PbS quantum dots . Moreover, MoS 2 /Si, MoS 2 /GaAs, MoS 2 /b‐P,, MoS 2 /WSe 2 WSe 2 /SnS 2 , WSe 2 /GaSe, and G/MoTe 2 heterostructures with high responsivity have also been demonstrated. Due to the ultrahigh photoresponsivity, objects in extremely weak light conditions as shown in Figure k, such as moonlight, and even starlight, could be detected by the highly sensitive heterostructure detectors.…”

Impact of edge structures on interfacial interactions and efficient visible-light photocatalytic activity of metal–semiconductor hybrid 2D materials

“…26 The characteristics of van der Waals heterostructures are represented not only by the constituent monolayers but also by the interactions among the layers. Recently, various types of van der Waals heterostructures based on MoS 2 have exhibited several interesting electrical, optical, and magnetic properties, [27][28][29][30][31][32][33][34][35][36][37][38][39] but none has reported the mechanism of interface interactions (vdW heterostructures) between MoS 2 and Si 2 BN. We have chosen a 2D Si 2 BN (ref.…”

Photo-tunable transfer characteristics in MoTe2–MoS2 vertical heterostructure

“…In recent years, van der Waals (vdW) heterostructures based on transition metal dichalcogenides (TMDs) are being studied extensively, due to their excellent electronic and opto-electronic properties [1][2][3][4] with potential applications such as transistor, 5 photo detector, 6,7 light-emitting diode (LED), [8][9][10] and solar cells. 11,12 Atomically sharp interfaces with intralayer high carrier mobility and lack of dangling bonds result in unique spatial charge separation 13 between the layers, as well as produce long-lived interlayer excitons 14 under light exposure.…”