Hybrid Metal-Semiconductor Nanostructure for Ultrahigh Optical Absorption and Low Electrical Resistance at...

Engineered optoelectronic surfaces must control both the flow of light and the flow of electrons at an interface; however, nanostructures for photon and electron management have typically been studied and optimized separately. In this work, we unify these concepts in a new hybrid metal-semiconductor surface that offers both strong light absorption and high electrical conductivity. We use metal-assisted chemical etching to nanostructure the surface of a silicon wafer, creating an array of silicon nanopillars protruding through holes in a gold film. When coated with a silicon nitride anti-reflection layer, we observe broad-band absorption of up to 97% in this structure, which is remarkable considering that metal covers 60% of the top surface. We use optical simulations to show that Mie-like resonances in the nanopillars funnel light around the metal layer and into the substrate, rendering the metal nearly transparent to the incoming light. Our results show that, across a wide parameter space, hybrid metal-semiconductor surfaces with absorption above 90% and sheet resistance below 20 Ω/□ are realizable, suggesting a new paradigm wherein transparent electrodes and photon management textures are designed and fabricated together to create high-performance optoelectronic interfaces.