A tin oxide/silicon heterojunction with a nano litchi shell structure for ultrafast, high-detectivity, self-powered broadband photodetectors

Abstract

Self-powered photodetectors with excellent figures-of-merit, fast response speed, and broadband detection capability have drawn tremendous research interest. However, it is still challenging to develop excellent light-absorbing materials as photodetectors with effective separation of carriers. In this paper, we develop a SnO₂ nano litchi shell structure/n-Si heterojunction with enhanced broadband light absorption for self-powered photodetection. The advantageous photoresponse performance of the SnO₂ nano litchi shell structure/n-Si heterojunction is attributed to the following factors: (1) the SnO₂ nano litchi shell structure has a large specific surface area to trap light; (2) the spherical cavity structure increases the light utilization rate by scattering and multiple reflections; (3) the significant Fermi energy difference at the junction of the SnO₂ layer and Si layer. As a result, the device exhibits a broadband detection capacity from ultraviolet (365 nm) to near-infrared (980 nm) at 0 voltage. Under 900 nm (10 μW cm⁻²), the photodetector shows the responsivity of 0.033 A W⁻¹, the photosensitivity of 8.35 × 10⁸ cm² W⁻¹, the detectivity of 2.94 × 10¹² Jones, the response time of 20.8 μs, and the recovery time of 285 μs. We also evaluated the near-infrared low signal imaging and fluorescence detection capability of the device. We expect that the SnO₂ nano litchi shell structure/n-Si heterojunction photodetector will have great potential in biomedical and environmental monitoring, and military reconnaissance.