Auger recombination in self-assembled quantum dots

• Applicants: Privatdozent Dr. Martin Geller; Dr. Arne Ludwig
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 566915888

The Auger effect is an electron-electron scattering process that plays a central role in both material analysis (Auger spectroscopy) and the optical properties of semiconductor nanostructures. This effect has been extensively studied in colloidal nanoparticles, where it degrades the optical properties due to non-radiative energy dissipation. In contrast, the Auger effect in single, self-assembled quantum dots has been studied only to a limited extent so far. The focus of this project is the investigation of the Auger effect in these quantum dots as an ideally controllable model system. The goal is to gain a deeper understanding of the underlying physical mechanisms and thus develop a more comprehensive picture of the Auger effect in all semiconductor-based quantum structures. To achieve this, different quantum dot structures will be specifically fabricated and electrically/optically characterized (project partner: Bochum) before being analysed for their Auger rates using resonance fluorescence techniques (project partner: Duisburg-Essen). In particular, samples with different quantum dot shapes, sizes, and compositions will be studied, as well as systems without electronic states in a wetting layer or without mechanical strain. Additionally, external magnetic and internal electric fields will be applied to investigate the influence of the Auger effect on the coherence time and dynamics of the spin states. The strength of the Auger process between two adjacent quantum dots in a quantum dot molecule will also be determined. These investigations will provide a detailed understanding of the impact of the Auger effect on linewidths, coherence times, blinking, and emission intensities. Moreover, they will identify ways to control or suppress Auger recombination through external and internal parameters. A comprehensive understanding of the Auger effect is crucial for the development of highly efficient single-photon sources with long coherence times; not only for emitters in self-assembled quantum dots but also in defect centers or two-dimensional van-der-Waals heterostructures. The knowledge gained from the experiments in this project will provide valuable input for theoretical modelling of the Auger effect in different material platforms that can be used for single-photon emitters, which will play a key role in future applications of quantum information processing.

• DFG Programme: Research Grants