Dislocation nucleation and propagation in Si0.95Ge0.05 layers on silicon

Defect reveal etching has been used to study the onset of relaxation in strained Si0.95 Ge0.05 layers grown by molecular beam epitaxy on (001) silicon substrates. Etch features corresponding to nucleation centers and to interfacial and threading segments of mismatch dislocations have been observed at thicknesses well below the expected critical thickness. From these it is deduced that mismatch dislocations take the form of half-loops on {111} planes which glide approximately symmetrically outwards from existing defects along the 〈110〉 directions parallel to the interface.