From single atoms to layered semiconductors: unraveling electronic behavior at the smallest scale
Julian Zanon defended his PhD thesis at the Department of Applied Physics and Science Education on May 18.
Julian Zanon has developed advanced theoretical models to understand how individual atomic defects and layered semiconductor structures influence electronic and spin behavior. His work bridges fundamental physics and device design, providing new insights that are relevant for future semiconductor technologies.
Visualizing a single atomic defect in silicon
At the atomic scale, even a single impurity can drastically alter the properties of a material. Zanon studied so-called acceptor states in siliconz, electronic states created by individual atomic defects. Using a multiband 办路辫 model, he was able to explain previously puzzling experimental images showing square ring鈥搇ike patterns observed with scanning tunneling microscopy.
His calculations revealed that these patterns correspond exactly to the spatial probability distribution of the acceptor ground state, confirming that these measurements represent the first direct images of such defect states in silicon. This provides a deeper understanding of how atomic-scale imperfections influence semiconductor behavior.
Spin鈥揷harge interactions around single impurities
In addition to silicon, Zanon investigated manganese impurities in III鈥揤 semiconductors such as GaAs. These impurities introduce complex interactions between electron charge and spin. By extending his theoretical model to include spin coupling effects, he uncovered unexpected correlations between spin and charge that go beyond classical descriptions.
One striking result is that these impurities can generate localized magnetic fields, with measurable effects even several nanometers away from the atom. This finding highlights the potential of single impurities as building blocks for future spin-based electronic devices.
Understanding layered semiconductor structures
The second part of the thesis focuses on antimonide-based superlattices, layered semiconductor structures widely used in optoelectronic devices. Zanon analyzed InAs/InAsSb superlattices to determine key material parameters, such as the valence band offset, which governs how charge carriers move across layers.
By combining theoretical predictions with experimental data, he identified accurate values for these parameters and showed how growth imperfections can influence optical properties. Such insights are essential for optimizing semiconductor structures used in detectors and lasers.
Toward improved infrared laser designs
Finally, Zanon applied his models to the design of intercascade lasers, devices used for infrared light generation. By comparing different layer configurations, he demonstrated that a V-shaped design significantly reduces optical losses compared to conventional structures.
This improvement makes the proposed design a promising candidate for efficient mid-infrared laser applications, which are important for sensing, environmental monitoring, and spectroscopy.
Bridging fundamental physics and device applications
By combining analytical theory with experimental validation, Zanon鈥檚 work shows how atomic-scale physics directly impacts real-world semiconductor devices. From visualizing single defects to optimizing layered structures, his research provides tools and understanding that support the development of next-generation electronic and photonic technologies.
-
Supervisors
Michael Flatt茅 & Paul Koenraad