Surface engineering assisted hot electrons injection for highly sensitive plasma photodetector

The plasmonic structure, with its unique local field enhancement effect, exhibits significant potential for enhancing the photoelectric conversion efficiency of micro-nano optoelectronic devices. However, the inherent interface defect issue in the traditional structural design of plasmonic devices strongly inhibits the utilization efficiency of high-energy hot electrons induced by plasmons. Herein, we develop a surface engineering strategy involving the intervention of an Al2O3 layer, which enables highly sensitive optoelectronic detection. The Al2O3 layer effectively suppresses interface defects during plasma photodetector construction, thereby improving hot electrons injection efficiency, which is confirmed by Raman spectra and finite-difference time-domain (FDTD) simulation. Meanwhile, the tensile strain introduced by the Al2O3 layer achieves near-field enhancement by increasing the contact area between Au nanoparticles and MoS2, thereby improving the photoelectric conversion efficiency of the device. Compared with the pristine MoS2 photodetector, the MoS2/Au/Al2O3 photodetector achieves a high responsivity of 2470 A/W, an excellent detectivity of 1.3 × 1010 Jones, and an ultra-fast response speed of 120 ns. This work provides beneficial design ideas for the development of highly sensitive plasmonic photodetectors.