High-quality Ge1-xSnx thin films on InGaAs buffer layers have been demonstrated using low-temperature growth by molecular beam epitaxy. X-ray diffraction and secondary ion mass spectrometry are used to determine the strain and Sn concentration. Up to 10.5% Sn has been incorporated into the Ge1-xSnx thin film without Sn precipitation, as verified by transmission electron microscopy. Roughened surfaces are found for tensile strained Ge1-xSnx layers. (c) 2012 Elsevier B.V. All rights reserved.