Substrate-dependent broadband light absorption in transferrable single nanowires

We studied broadband light absorption in laterally oriented single Si nanowires placed on metallic and dielectric substrates. Finite-difference timedomain simulation showed that when a Ag bottom mirror was adjacent to a Si nanowire, the optical resonances were significantly amplified at every resonant wavelength beyond the classical limit given by ray optics, thereby significantly enhancing the absorption efficiency. In particular, an omnidirectional Ag mirror was effective for sustaining two-dimensional whispering-gallery modes marginally excited using a dielectric substrate. The results of this numerical investigation will provide useful information for designing nanowire platforms for next-generation solar cells.