Reports of photoluminescence from GeSn grown on Ge substrates by molecular beam epitaxy have been limited. We find that one limiting factor to observing photoluminescence is due to localized defect states marked by photoluminescence at 2400 nm and originating from the Ge substrate and buffer layer. In this study, we report on an optical study utilizing doped Ge(001) substrates to effectively suppress defect-related photoluminescence in GeSn layers by filling localized defect trap states. For this experiment, a GeSn layer with Sn content up to 10.5% was grown on a doped Ge(001) substrate. Analysis of the physics of the photoluminescence spectrum collected from the GeSn thin film shows an emission at the expected wavelength of 2300 nm for 10.5% Sn content and the absence of the typically observed defect related signal at 2400 nm. This understanding is further confirmed using short pulse optical excitation of the GeSn grown on undoped Ge substrates.
@article{arxiv.2508.13027,
title = {Neutralizing Optical Defects in GeSn},
author = {Nirosh M. Eldose and Dinesh Baral and Diandian Zhang and Fernando Maia de Oliveira and Hryhorii Stanchu and Mohammad Zamani-Alavijeh and Yuriy I. Mazur and Wei Du and Shui-Qing Yu and Gregory J. Salamo},
journal= {arXiv preprint arXiv:2508.13027},
year = {2025}
}