Enhanced Photoresponsivity by Photovoltaic Effect in MoS₂/WSe₂ Heterostructure

There are various types of photosensors that can be classified according to sensing mechanisms such as photoelectric or photochemical effects, or various performance metrics such as spectral responses. Two-dimensional transition metal dichalcogenides (2D TMDs), such as MoS2 and WS2, are widely known as photoabsorbent material in photodetectors. Most of the reported MoS2 photodetectors has disadvantages of quantitative control due to their photo gating effect. These devices typically suffer from poor responsivity and response speed and low on/off ratio. To solve these shortcomings, van der Waals (vdW) heterostructures can be utilized. Van der Waals heterostructures provide a unique platform for next-generation optoelectronics with unique flexibility and high performance with two-dimensional materials integrated with a variety of functional materials<br/><br/>In our study, we demonstrated a high-response photodetector with MoS₂/WSe₂ heterostructure on Al₂O₃ insulator. While using single layer MoS₂ as a channel, a photodetector is fabricated by covering MoS₂/WSe₂ van der Waals (vdW) heterostructure, which facilitates efficient separation and transportation of photogenerated carriers based on photovoltaic effect. By fabricating MoS₂/WSe₂ heterostructure on top of Al₂O₃insulator, the photodetector can get higher on-off ratio and high responsivity. It shows a high responsivity of 80 mA/W and 30 mA/W with a 638 nm laser, which is 20-times higher than traditional MoS₂ photodetectors, and it also demonstrates the advantage of an improvement in photocurrent ratio resulting from the enhancement of on-current by more than 10-times. This mechanism is expected to be applied to increase the efficiency of photodetectors as well as electric devices such as solar cells