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: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 537010567

Aim of this work is the realization of an all-Semiconductor, CMOS-compatible MIR Detector. Therefore plasmonic antennas made of heavily doped group IV semiconductors shall be utilized. Inside these antennas hot electrons get generated by the plasmonic mode decaying which than can be measured as a photocurrent. The use of group IV semiconductors as active plasmonic materials is a viral field of investigation. Besides the possibility of being fully integrable into a CMOS-process another advantage is the high field confinement of group IV semiconductors in comparison to gold or silver. To tackle this goal the special electrical field distribution of plasmonic modes needs to be investigated. Therefore the influence of the three dimensional antenna geometry as well as the underlying substrate needs to be investigated. With this knowledge a ideal three dimensional antenna geometry shall be found to create an MIR detector. As a first step an ideal material for this task needs to be identified. For the characterization of different materials reflection measurements will be performed. Out of the reflection data the permittivity as well as the specific Drude-parameter of the materials can be extracted by using the Kramers-Kronig relation. These parameters can be used to benchmark the usability of the different materials. The obtained parameters can further be introduced into an FDTD simulation toll to investigate the plasmonic behavior of antennas produced out of these material. With these simulations an ideal three dimensional antenna geometries shall be found. An ideal geometry herby means the formation of a compact an high field enhancement introduced by the plasmonic antennas. With the simulations it will be investigated how the geometry as well as the underlying substrate influences the spatial distribution of the electrical filed, to gain a deeper understanding of the field distribution itself. Using standard nano-fabrication steps like electron beam lithography e.g. these antennas will be fabricated and firstly investigated via FTIR spectroscopy. These first steps can be performed in a feed-back loop to iteratively find the ideal material and geometry combination. Finally a proof of concept device shall be fabricated and characterized via opto-electrical measurement. Therefore the device will be mounted into a cryostat and electrically contacted. The cryostat itself can be inserted into an IR Microscope measuring set up. In this way the electrical response of the device to an optical signal can be detected as a function of time and temperature and the response time can be measured.

• DFG Programme: WBP Fellowship
• International Connection: Italy
• Hosts: Professorin Dr. Leonetta Baldassarre; Professor Dr. Michele Ortolani