Epitaxial growth and crystalline properties of Ge1−x−ySixSny on Ge(0 0 1) substrates

We have investigated the influence of tensile and compressive strain on the crystalline structures of Ge1−x−ySixSny epitaxial layers. The tensile strain in Ge1−x−ySixSny induces a non-uniform crystallinity of (2 2 0) lattice planes and surface roughening despite the strain magnitude is as small as 0.20%. In contrast, the unstrained or compressive strained Ge1−x−ySixSny layer exhibits a flat and uniform surface and high crystallinity. We found that the control of the sign of the strain is an important factor to obtain a high quality Ge1−x−ySixSny layer. Furthermore, substitutional Sn atoms in Ge1−x−ySixSny epitaxial layer with an Sn content of 10% are thermally stable for annealing at 500 °C.