Benchmarking the Use of Heavily Doped Ge for Plasmonics and Sensing in the Mid-Infrared

Despite the recent introduction of heavily doped semiconductors for mid-infrared plasmonics, it still remains an open issue whether such materials can compete with noble metals. A whole set of figures of merit are employed to thoroughly assess the use of heavily doped Ge on Si as a mid-infrared plasmonic material and benchmark it against standard noble metals such as Au. A full-wave electrodynamics framework is used to model and design high-performance, silicon-foundry compatible mid-infrared plasmonic sensors based on experimental material data reaching plasma wavelengths down to λp ∼ 3.1 μm. It is finally shown that Ge sensors can provide signal enhancements for vibrational spectroscopy above the 3 orders of magnitude, thus, representing a promising alternative to noble metals, leveraging the full compatibility with the silicon foundry microfabrication processes.