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 degrees 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) over bar 1 0] and < 1 1 2 > at the Ge1-xSnx/Ge(1 1 0) interface. We found that the propagation of 60 degrees dislocations preferentially occurs, which contributes to the strain relaxation only for the [0 0 1] direction. (c) 2013 Elsevier Ltd. All rights reserved.