Benchmarking the use of heavily-doped Ge against noble metals 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 point whether such materials can compete with noble metals. We employ a whole set of figures of merit 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. In doing this, we design and model high-performance, CMOS compatible mid-infrared plasmonic sensors based on experimental material data reaching plasma frequencies up to about 1950 cm-1. We demonstrate that plasmonic Ge sensors can provide signal enhancements for vibrational spectroscopy above 3 orders of magnitude, thus representing a viable alternative to noble metals.