Si–MoS2 Vertical Heterojunction for a Photodetector with High Responsivity and Low Noise Equivalent Power

In this study, we propose the fabrication of a photodetector based on the heterostructure of p-type Si and n-type MoS2. Mechanically exfoliated MoS2 flakes are transferred onto a Si layer; the resulting Si–MoS2 p–n photodiode shows excellent performance with a responsivity (R) and detectivity (D*) of 76.1 A/W and 1012 Jones, respectively. In addition, the effect of the thickness of the depletion layer of the Si–MoS2 heterojunction on performance is investigated using the depletion layer model; based on the obtained results, we optimize the photoresponse of the device by varying the MoS2 thickness. Furthermore, low-frequency noise measurement is performed for the fabricated devices. The optimized device shows a low noise equivalent power (NEP) of 7.82 × 10–15 W Hz–1/2. Therefore, our proposed device could be utilized for various optoelectronic devices for low-light detection.