Exploring GeSn films for advanced optoelectronics

Researchers from the Tufts Renewable Energy and Applied Photonics (REAP) Labs recently published a paper, “Temperature-Dependent Dielectric Response, Index of Refraction, and Absorption Coefficient of GeSn Films up to 8.4% Sn”, in IEEE Xplore. The research team included Professor and Chair of the Department of Electrical and Computer Engineering Thomas Vandervelde, Kevin Grossklaus, a technical staff scientist at MIT Lincoln Laboratory who was previously a Tufts research assistant professor and laboratory manager, and Amanda Lemire, a joint PhD student in mechanical engineering and materials science and engineering. 

The study focused on understanding the optical properties of germanium tin (GeSn) thin films, a promising material for optoelectronic applications. Using spectroscopic ellipsometry, the researchers measured three fully strained Ge(1-x)Snx films with varying tin compositions (3.6%, 6.5%, and 8.4%) deposited on a Ge substrate. They examined the films across a broad energy range and at temperatures ranging from 78K to 475K. Their findings revealed how tin content and temperature influence the band structure, including a notable red-shift in critical point energies and the discovery of an additional critical point in GeSn that does not appear in pure Ge.

This research highlights the real-world potential of GeSn films in advanced optoelectronic devices, including photodetectors, photoconductors, and infrared light emitters. By optimizing the optical properties of GeSn alloys, their work could contribute to the development of more efficient and versatile technologies, spanning applications in imaging, communication, and energy systems

Learn more about REAP Labs at Tufts.