Investigation on the Preparation and Performance of InSe Nanosheets/Si Heterojunction Photodetectors

InSe nanosheet/Si mixed-dimensional p–n heterojunction optoelectronic detection devices were fabricated. It was observed that the InSe nanosheets/Si heterojunction devices exhibit excellent rectifying characteristics with a current of only 0.7 nA at a bias of −3 V. This confirms the formation of a robust vdW p–n heterojunction between InSe nanosheets and Si. The built-in electric field of the heterojunction prevents the generation of a reverse bias current, achieving a current switching ratio of 600 at ± 3 V biases. Under illumination with blue light (405 nm) and red light (650 nm), significant photocurrent responses were obtained, generating light currents of 432 nA and 1132 nA. The device’s dark current is merely 0.5 nA, resulting in a maximum light current switching ratio of 2260, under a bias voltage of −2 V. The responsivity under blue light illumination is 1.18 A/W with an external quantum efficiency (EQE) of 362%, and the detectivity is 8.4 × 1010 Jones. Under red light illumination, the responsivity is 19.65 A/W with an EQE of 3751%, and the detectivity is 1.4 × 1012 Jones. Additionally, encapsulating the device surface with PMMA can isolate interference from the external environment, enhancing the device’s photocurrent. Compared to InSe nanosheets, the InSe nanosheet/Si heterojunction exhibited faster response speed, with rise and fall times of 0.15 and 2.5 ms.