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.