Vertical Tip-to-Tip Interconnection p–n Silicon Nanowires for Plasmonic Hot Electron-Enhanced Broadband Photodetectors

A p–n junction photodetector, formed between the tip-to-tip interconnection of vertical silicon nanowire arrays, was fabricated by using a facile and economic process with remarkable performances. Through the steady trend of the current–voltage curve, it is proven that the reliable welding between p- and n-type silicon nanowire tips was realized by using Joule heating. The photodetector exhibits a typical rectifying behavior with light off and excellent photoresponse characteristic with light on. Further photoresponse analysis indicates that the photodetector can work well over a broad range of wavelengths from visible light at 650 nm to near-infrared at 2200 nm, where the normalized highest I light/I dark ratio of 1048.6 has been confirmed at 0 V bias voltage under irradiation at 650 nm due to a super low dark current of ∼0.03 nA and high responsivity. The responsivity (R), normalized detectivity (D*), and rise/fall time are calculated to be ∼25.11 mA/W, ∼1.03 × 1010 cm Hz1/2 W–1, and 0.31/0.3 ms, respectively. In addition, the physics mechanism model was proposed to elucidate where the photocurrent originates and how it evolves under different wavelengths with zero bias voltage, which shows that the coexistence of p–n and Schottky junctions could effectively separate the electron–hole pairs induced by incident light with wavelengths of less than 1100 nm and drive the plasmonic hot electrons in silver nanodots into p-type silicon under all wavelengths, respectively.