Epitaxial growth of Ge1-xSnx on c – Plane sapphire substrate by molecular beam epitaxy

In this paper, we have demonstrated the first epitaxial growth of Ge<inf>1-x</inf>Sn<inf>x</inf> on c – plane Sapphire. This has been achieved by growing Ge<inf>1-x</inf>Sn<inf>x</inf> on Ge(1 1 1)/AlAs/Al<inf>2</inf>O<inf>3</inf>(0 0 0 1) engineered substrates by low-temperature molecular beam epitaxy. The growth starts with three-dimensional islands growth, characteristics of the Volmer – Weber growth mode. The presence of type A and type B oriented domains of Ge<inf>1-x</inf>Sn<inf>x</inf> epilayers was shown by reflection higher energy electron diffraction analysis. High-resolution X-rays diffraction measurement shows that the grown crystals are tetragonally strained. Further, from the recorded pole figure measurement of the two grown samples, the additional presence of reflection micro-twins was also revealed. The presence of twining has been significantly increased for the case of the sample grown with a higher Sn percentage of 5.2%, as compared to that of the one grown with 3.6% of Sn. However, the presence of defects in the epilayers may be suppressed by growing significantly a thicker layer.