Ultra-broadband photoresponse of localized surface plasmon resonance from Si-based pyramid structures

Structures capable of exciting localized surface plasmon resonance (LSPR) have been widely utilized to increase photoresponse in many photoactive devices. However, most LSPR can be induced in only a small spectral range and with particular polarization. Here, LSPR with ultra-broadband response is revealed. Light detection using such LSPR is also explored to exhibit a spectral range covering the visible to mid-infrared. The strong LSPR induced by the inverted pyramid array structure enables a Si-based Schottky photodetector to detect photons even with energy lower than the Schottky barrier height, leading to the experimental measurement covering from 300 to 2700 nm. Theoretical evaluation even predicts a response beyond 4000 nm.