In this work, we demonstrate that it is possible to use III-V semiconductors for plasmonics from the THz up to the midinfrared spectral range. We have fabricated hyperbolic nano-antenna based on heavily doped semiconductors demonstrating localized plasmon modes. This hyperbolic nano-antenna is 10 times: 10 nm doped InAs / 10 nm undoped GaSb. The free carriers are confined in the 10 nm layer of InAs. The confinement shifts the effective plasma frequency of the metamaterial towards the high frequencies, extending the possibility to probe molecules until 2000 cm-1 , thus covering the complete fingerprint frequency range for molecular and biosensing applications. The nano-structuration of the hyperbolic material allows to access two main plasmonic resonances at 800 cm-1 and 2000 cm-1 . This bimodal property is appealing to detect and identify biomolecules over a large spectral range. With these hyperbolic nanoantennas, we can either enhance the absorption of rovibrational modes of molecules with surface-enhanced infrared absorption (SEIRA) spectroscopy1 or enhance the thermal emission of molecules with surface-enhanced thermal emission spectroscopy (SETES)2
In this paper, III-IV semiconductors are demonstrated as strong candidates for plasmonics applications in the Mid-IR. The perfect absorbers (PA) fabricated with heavily doped semiconductors features strong coupling between Fabry-Perot and localized surface plasmon modes. Also, anisotropic nano-antenna fabricated at the top surface yield a huge anisotropy to the polarized light. The fabricated PA with 2D periodic arrays of rectangular nano-antenna is presented, where the rectangular shape allows one to excite localized surface plasmon resonances (LSPR) at different wavenumbers depending on the polarization of the incident light. Preliminary results of the bio-functionalization through phosphonic acid are shown for the PA aditionnally. Furthermore, it becomes clear that it is possible to detect bio-molecules of interest even far in the infrared on a very small surface and with a few hundreds of nano-antenna.
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