Séminaire

Mardi 22 Septembre 2026 à 11h00.

Non-local heating in semiconductor membranes

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Heating of photonic and electronic semiconductor devices limits their performance and lifetime. To counteract this, any thermal management should start in close proximity to the heat source. It is a common assumption that the heat source (e.g., a laser spot) and the resulting heat spot locally coincide for length scales exceeding the mean free paths of the dominant heat carriers (phonons in most semiconductors). In this talk, it will be shown that this paradigm of heat locality can break down on a few micrometer length scale and non-local heating appears. The required thermal imaging is based on two-laser Raman thermometry (2LRT) implemented in fully customized setups. First, these setups were tested by probing bulk material and membranes made of Si [1] and GaN [2]. Subsequently, geometries such as edges, corners, and hexagons were etched into GaN membranes. In addition to the common laser-induced heat spot, the heating of boundaries (semiconductor / vacuum interfaces) was observed in the GaN samples a few micrometers away from the laser spot at temperatures > 295 K [3]. Phonons with long mean free paths are generated in the laser-induced heat spot and partially propagate to the sample boundaries. Here, these phonons scatter and deposit their thermal energy, leading to non-local heating. This observation highlights the importance of the particular heat generation process (e.g., via light absorption in a semiconductor) for modeling thermal transport. In addition, boundaries appear in any real-world device and should be considered for thermal management.

[1] K. Dudde, M. Elhajhasan, G. Würsch, J. Themann, J. Lierath, D. Paul, N.H. Protik, G. Romano, and G. Callsen, Material Today Physics 57, 101784 (2025).
[2] M. Elhajhasan, W. Seemann, K. Dudde, D. Vaske, I. Rousseau, T. F. K. Weatherley, J.-F. Carlin, R. Butté, N. Grandjean, N. H. Protik, G. Romano, and G. Callsen, Phys. Rev. B 108, 235313 (2023).
[3] M. Elhajhasan, E. Trukhan, K. Dudde, G. Würsch, J. Lierath, I. Rousseau, R. Butté, N. Grandjean, N. H. Protik, G. Romano, and G. Callsen, arXiv:2604.19203 (2026).

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