Hot Electron Generation in Silicon Micropyramids Covered with Nanometer-Thick Gold Films for Near-Infrared Photodetectors

Plasmonic metallic nanostructure/silicon composite gains increasing attention due to their NIR photodetection capability and potential compatibility with the CMOS technology. However, those kinds of photodetectors suffer from low efficiency due to the low optical absorption and poor hot electron injection efficiency. Here, we propose an efficient and low-cost NIR photodetector based on gold film coated silicon micro-pyramid, which was fabricated with the large-scale, lithography-free chemical wet-etching process. We experimentally demonstrated the proposed micro-pyramid enhanced the photoresponsivity for the NIR light by 3 times compared with that of the flat reference sample at 1300 nm. Besides, the micro-pyramid strategy allowed the photodetector preserve polarization-insensitive and incident angle-insensitive photoresponse. Furthermore, we further increased the responsivity through the backside illumination from the silicon side and carefully investigated the background mechanism by changing the thickn...