A complementary metal-oxide-semiconductor (CMOS) -compatible Germanium (Ge)/Silicon (Si) system holds the promise for compact, low-cost and simple connection to on-chip data storage, processing and/or communication systems based on mainstream Si-based microelectronics. At terahertz (THz) frequencies, the plasmonic properties of n-doped Ge enable localized surface plasmon resonances (LSPR) in bow-tie antennas that can be used for a state-of-the-art biosensing platform, and that in the future could integrate in microfluidics for lab-on-a-chip application.
In this work, we show the polarization-sensitive plasmonic resonance of highly doped Ge antennas and demonstrate an increase of the antenna quality factor (Q-factor) by Fano coupling of bright and dark modes. The dark mode is a traveling wave confined to the antenna substrate. The coupling of the bright mode (antenna resonance) to the dark mode is demonstrated as the substrate thickness is gradually changed. Moreover, we also report on the effect of different packing densities of antennas per mm2 and a direct dependency of the antenna density on the transmission is demonstrated.
Finally, Ge antennas on a highly-resistive silicon dioxide (SOI) substrate have no detrimental effect to bright-dark coupling and, with respect to antennas on Si substrate, show a Q-factor enhancement of ~21% for antennas without and of ~43% for antennas with Fano coupling. We believe these results could pave the way to a CMOS-integrated, low-cost biosensor platform.
|Solid State (Experiment)