Infrared Plasmon-Polariton Modes in Hyperbolic Metamaterials Made from III-V Semiconductor Multilayers

While ionic crystals provide natural low-loss infrared hyperbolic resonances through the excitation of phonon polaritons, their operational bandwidth is limited to a few hundred wavenumbers (cm^-1) or tens of meVs. The integration of these materials with large-scale infrared optoelectronic devices also presents its own challenges. We implement an ultrawide low-loss Type I hyperbolic metamaterial covering a spectral bandwidth of 2000 cm^-1 for wavelengths longer than 5.3 μm. We produced the hyperbolic metamaterial with a stack of intercalated heavily-doped InAs and undoped InAs epilayers grown by molecular beam epitaxy. The heavy doping was accomplished with Tellurium to obtain electron concentrations of 10¹⁹ cm^-3 and the optical properties of this stack were measured by infrared ellipsometry. The materials were then dry etched to form one-dimensional square gratings (with periods from 2 to 10 μm) and modeled by finite element electromagnetic calculations (COMSOL). The models agree with measurements, showing the formation of hyperbolic plasmon polaritons at the same frequencies where experimental features were observed. Additionally, we identified an Epsilon Near Zero mode associated with long-range surface plasmon polaritons contained in the dielectric layers. This work demonstrates that highly subdiffractional light confinement can be achieved with a metamaterial that can be integrated with III-V semiconductor infrared devices such as photodetectors and emitters.