Localized surface plasmon resonance breaking the photodetection limit of si-based schottky photodetector

Abstract

Nowadays, compound semiconductors are the main approach to detect mid-infrared (IR) light, such as HgCdTe and InAsSb, due to the bandgap tunability compared with Si. However, the epitaxy processes are expensive and energyintensive. Also, compound devices are not compatible with Si-based IC manufacturing. To solve those problems, here, we apply inverted pyramid array structures (IPAS) to induce localized surface plasmon resonance (LSPR) for Si-based Schottky devices. While IR illuminates metal covered IPAS (metal-IPAS), the photo-electrons can accumulate photon energy repeatedly through IPAS induced LSPR. While the electron energy is large enough to overcome the Schottky barrier, so the photo-current is generated. Regarding device preparation and measurement, briefly, the IPAS were formed on n-type Si (n-Si) substrates through photolithography, dry etching, and wet etching. Afterward, 10-nm-thick Ag films and 100-nm-thick Ag grid anode were thermally deposited on the IPAS successively to form Schottky junctions. Finally, Al was thermally deposited on the back of n-Si wafers to be the cathode. After device fabrication, the devices were illuminated by a 4010 nm mid-IR pulse laser, generated from a 1064 nm pulse laser through an optical parametric generator. The photo-voltage of the device induced by the mid-IR was measured by an oscilloscope. Consequently, the oscilloscope showed a short pulse while the device was illuminated by the 4010 nm pulse laser. The rising time is 8 ns, and the amplitude is 10.2 mV. The result reveals that the metal-IPAS induced LSPR successfully detects mid-IR light with photon energy less than Schottky barrier height ? ? 2021 SPIE.