[WeA1] Epitaxy of Novel Optical Materials

9:15 AM - 9:30 AM JST(12:15 AM - 12:30 AM UTC)

[WeA1-03] Germanium-Tin Thin Films and Nanostructures for Sustainable Group-IV Photonics

〇Reyhaneh Ramezani¹, Andrea Giunto¹, Leo Webb¹, Nuño Amador-Mendez¹, Ludovica Lunghi¹, Ivan Sinev³, Hatice Altug³, Kirsten Emilie Moselund^4,5, Anna Fontcuberta i Morral^1,2 (1. Lab. of Semiconductor Materials, Inst. of Materials, École polytechnique fédérale de Lausanne (EPFL), Univ. (Switzerland), 2. Inst. of Physics, École polytechnique fédérale de Lausanne (EPFL), Univ. (Switzerland), 3. Bionanophotonic Systems Lab., École polytechnique fédérale de Lausanne (EPFL), Univ. (Switzerland), 4. Integrated Nanoscale Photonics and Optoelectronics Lab., Inst. of Photonics, École polytechnique fédérale de Lausanne (EPFL), Univ. (Switzerland), 5. Lab. of Nano and Quantum Tech., Paul Scherrer Inst. (PSI) (Switzerland))

Germanium–tin (GeSn) alloys are CMOS-compatible group-IV semiconductors for infrared photonics in the telecom band. With sufficient Sn incorporation, GeSn becomes a direct bandgap material, enabling absorption and emission beyond 1550 nm. However, achieving high Sn contents remains challenging due to strain, defect formation, and Sn segregation, which strongly affect the optical response. In this study, GeSn thin films (~350 nm) with varying Sn contents are deposited by magnetron sputtering on Ge and Si substrates. X-ray diffraction and reciprocal space mapping show Sn incorporation up to ~8 at.% on Ge, with pseudomorphic growth, while GeSn on Si reaches Sn contents up to ~12 at.% and is partially relaxed. Optical properties are investigated using a parameterized semiconductor oscillator model for spectroscopic ellipsometry and FTIR-based absorption analysis is used to estimate bandgap in relaxed and strained GeSn thin films. The final aim is to identify how composition, strain, and defects control the optical response of GeSn thin films for a pathway toward GeSn-based photodetectors and emitters in the telecom band.