Epitaxial growth and anisotropic strain relaxation of Ge1−xSnx layers on Ge(1 1 0) substrates

We have investigated the strain relaxation behavior and dislocation structures of Ge1−xSnx epitaxial layers on Ge(1 1 0) substrates. We found that the anisotropic strain relaxation of a Ge0.966Sn0.034 layer along the [0 0 1] direction preferentially occurs during postdeposition annealing over 500 °C. Transmission electron microscopy observation revealed that the anisotropic strain relaxation is attributed to the propagation of misfit dislocations along the two directions of [1¯ 1 0] and 〈1 1 2〉 at the Ge1−xSnx/Ge(1 1 0) interface. We found that the propagation of 60° dislocations preferentially occurs, which contributes to the strain relaxation only for the [0 0 1] direction.

► We investigated the thermal stability of epitaxial GeSn on Ge(110). ► Sn precipitation hardly occurs even after annealing at 600°C for 10 minutes. ► The anisotropic strain relaxation of GeSn along the [001] direction occurs. ► We found the propagation of dislocations along the [1¯10] and <112> directions.