Tailoring plasmonic modes for all-semiconductor detectors in the mid-infrared

• Applicant: Dr. Fritz Berkmann
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: Funded in 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 537010567

• Final Report Year: 2025

Final Report Abstract

I have focused on the study of plasmonic modes with the perspective of developing all semiconductor detectors. The goal is to understand how a plasmonic antenna can produce a maximum of hot carriers in a narrow spectral band so that the antenna can act as a plasmonic enhanced photodiode. Therefore, GeSn was studied as a possible candidate for all-semiconductor plasmonic application. It could indeed be shown that GeSn is one of the most promising candidates for modern mid-IR plasmonics, while to address the lower wavelength range of the mid-IR spectra, Ti was investigated since it is fully CMOS compatible. In order to get a spectrally narrow extinction peak, the coupling of a Localised surface plasmon resonance (LSPR) and a Rayleigh anomaly (RA) forming a Surface Lattice Resonance (SLR) was used and we have shown that these modes can be optimised in order to obtain spectrally narrow features. Since the actual amount of activated hot carriers is strongly dependent on the damping mechanism of the plasmonic mode, the shape of the plasmonic antennas needs to be investigated to favour Landau damping. Therefore, 3D antenna geometry variations were investigated to see how a maximum of electrical field enhancement can be achieved. Simultaneously a fabrication scheme was developed that allows an easy adaption of the antenna geometries. For the final experiments a measurement set up was built inside the laboratory of La Sapienza. This set up consisted of a QCL IR laser that can be feed into a Cassegrain microscope. Inside this microscope a He-flow cryostat can be inserted to measure the samples at cryogenic temperatures. For the electrical connection the cryostat was equipped with 24 electrical lines that can be contacted over a custom-made switchbox to a lock in amplifier.

Publications

• Influence of material and geometry parameters on resonance linewidths of plasmonic modes in gratings made from highly doped Ge1− x Sn x. Journal of Physics D: Applied Physics, 57(43), 435103.
  Berkmann, Fritz; Povolni, Pavel; Schwarz, Daniel & Fischer, Inga A.