Local engineering of the electron-phonon scattering rate in graphene towards ultrasensitive graphene terahertz detectors

• Applicant: Florian Ludwig
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering ; Experimental Condensed Matter Physics
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 560725895

This proposal explores the potential of defect engineering in graphene to enhance terahertz (THz) detector performance, focusing on photothermoelectric (PTE) and resistive self-mixing (RSM) effects. The study aims to locally modify electron-phonon scattering through the strategic introduction of defects, achieving enhanced electron cooling via supercollision cooling processes. This approach, which leverages disorder-assisted scattering, is expected to yield substantial improvements in detector response and sensitivity at room temperature across a wide THz frequency range. The research pursues two main objectives: (1) to boost the PTE response of graphene-based THz detectors, achieving sensitivity levels that exceed those of current state-of-the-art terahertz field-effect transistors (TeraFETs), and (2) to enhance the operational detection bandwidth of recently developed graphene photomixers by minimizing electron cooling times through supercollision cooling. These goals will be pursued through the fabrication of two detector architectures: a control device based on pristine graphene and a defect-engineered device designed to maximize disorder-assisted cooling in certain device regions. By comparing these devices, we aim to dissect the respective contributions of the PTE and RSM effects under controlled defect densities. The project will employ advanced characterization methods, including Raman spectroscopy, electron microscopy, and time-resolved photocurrent measurements, to assess defect-induced cooling dynamics and PTE efficiency in graphene. This data-driven analysis will yield quantitative insights into the influence of supercollision processes on carrier temperature and energy dissipation, informing optimal defect configurations for future THz applications. Conducted at the Catalan Institute of Nanoscience and Nanotechnology (ICN2), this research is supported by state-of-the-art facilities and collaboration with internationally recognized experts. Findings from this study are expected to advance the frontier of THz detection technology, fostering the development of highly sensitive, broadband graphene-based THz detectors suitable for applications in spectroscopy, communications, and sensing. Moreover, this research will contribute to the fundamental understanding of supercollision cooling mechanisms in 2D materials, with implications for next-generation optoelectronic device engineering.

• DFG Programme: WBP Fellowship
• International Connection: Spain
• Host: Professor Dr. Klaas-Jan Tielrooij