Metal-insulator-metal antennas in the far-infrared range based on highly doped InAsSb

Plasmonic behavior in the far-infrared (IR) and terahertz (THz) ranges can facilitate a lot of applications in communication, imaging or sensing, security, and biomedical domains. However, simple scaling laws cannot be applied to design noble metal-based plasmonic systems operating at far-IR or THz frequencies. To overcome this issue, we numerically and experimentally explore the plasmonic properties in the spectral range between 25 and 40 μm (12 and 7.5 THz) of metal-insulator-metal (MIM) antennas made of InAsSb a highly Si-doped semiconductor. We demonstrate that these MIM antennas sustain a gap plasmon mode that is responsible for high light absorption. By tracking this peculiar plasmonic signature for various antennas' widths, we prove that Si-doped InAsSb microstructures realized on large areas by laser lithography and the wet etching process are a low cost, reproducible, and readily CMOS compatible approach.