Low-temperature growth of Ge1 − xSnx thin films with strain control by molecular beam epitaxy

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.

► GeSn alloys were grown by molecular beam epitaxy with up to 10.5% Sn.
► Unstrained GeSn alloys have high crystal quality.
► Consistent Sn concentration was obtained from two different methods.
► The growth of tensile strained GeSn results in a roughened surface.