Silicon-HgTe quantum dot broadband photodetectors via Ag nanoparticle interface engineering

Colloidal quantum dots (CQDs) enable heterogeneous integration with silicon, effectively extending spectra of silicon-based photodetectors to achieve broadband detection spanning from the visible to the infrared spectrum. In this study, we fabricated a broadband photodetector covering wavelengths from 400 nm to 2630 nm by stacking silicon photodiode with HgTe CQD photodiode. Conventional hetero stacking often leads to band mismatches and charge transport barriers at the interfaces, significantly constraining device performance. To mitigate these issues, we implemented interfacial engineering by introducing silver nanoparticles (Ag NPs) at the heterojunction conductive layer interface. This modification optimizes the interfacial band alignment, enhancing carrier mobility and separation efficiency, ultimately improving overall photodetector performances. Systematic screening of Ag NPs based on size and thickness revealed that a bilayer structure with a 10 nm diameter of Ag NPs achieved optimal enhancement. Compared to the reference device, the photogenerated current to dark current ratio increased by 430%. The total photocurrent density of the broadband detector showed a 27% improvement, with specific increases of 52% in the visible light region and 16% in the near-infrared region. Notably, the calculated specific detectivity reached 1.70 × 10¹¹ Jones at 2200 nm under room temperature conditions, accompanied by a fast response time of 10.8 μs and a 3 dB bandwidth of 275 kHz. Leveraging this high-performance broadband photodetector, we further developed a visible-to-infrared optical anti-counterfeiting and encryption system capable of high-fidelity data preservation.