Strain relaxation in epitaxial Ge crystals grown on patterned Si(001) substrates

In this paper we report on the defects formed in Ge crystals grown on Si(001) pillars upon strain relaxation. The analysis is performed by high-angle annular dark-field scanning transmission electron microscopy. The strain relaxation happens by means of 60° and 90° misfit dislocations with Burgers vectors b → = 1 2 ⟨ 110 ⟩ . Misfit dislocations may split forming partial dislocations with Burgers vectors b → = 1 6 ⟨ 112 ⟩ , and are separated by a stacking fault. Besides, intrinsic stacking faults in different {111} planes interact and annihilate each other forming stair rod dislocations. Coherent and incoherent twin boundaries of the Σ 3{111} and Σ 3{112} types are also found in the Ge.