Mid-infrared sensing using heavily doped germanium plasmonics on silicon substrates

Heavily-doped semiconductor films are very promising to produce mid-infrared plasmonic devices for a wide range of sensing applications because the real part of the dielectric function of the film is negative and broadly tunable in this wavelength range. In this work, we investigate, n-type doped Ge epilayers grown on Si substrates. We design and realize Ge nano-antennas on Si substrates demonstrating the presence of localized plasmon resonances, and exploit these resonances for molecular sensing in the mid-infrared.