Metallic nanostructures inclusion to improve energy harvesting in silicon

Abstract

New phenomena have been discovered at the nanoscale that allow us to manipulate light and design devices. Evanescent waves such as Surface Plasmon Polaritons are excited in dielectric–metal interfaces and propagate in the metal. If they reach other interfaces, they may be transmitted by the metal. It is a phenomenon known as Extraordinary Optical Transmission that occurs in nanostructures at the optical range. Depending on the metal it is possible to tune the wavelengths and incident angles where this phenomenon occurs. Gold, silver, aluminium and copper nanolayers are analysed on top of silicon (a-Si and c-Si) considering a sweep between 250 nm and 2500 nm. Considering a novel model based on Fresnel Coefficients in absorbing media, it is possible to improve energy harvesting in the ultraviolet–visible range, mainly due to the propagation of Surface Plasmon Polaritons. Then, the role of Surface Plasmon Polaritons in Air–Metal–Silicon nanostructures is analysed. The inclusion of the metal layer may decrease the reflectance by at least 10%, reaching values higher than 60%. The presented charts allow us to analyse the materials, wavelengths and incident angles where reflectance is decreased. There, the inclusion of metal layers brings benefits to the photodetection, since more energy is available in the absorbing layer. Considering this approach, the detection of specific wavelengths may be improved by introducing metals in the detectors.