Study of misfit-dislocation formation in strained-layer heteroepitaxy using ultrahigh vacuum scanning tunneling microscopy

The formation of misfit dislocations in epitaxial growth of 2.1% lattice-mismatched EuTe on PbTe (111) was studied using ultrahigh vacuum scanning tunneling microscopy. It is shown that at the critical layer thickness straight monolayer surface step lines appear as a result of glide of threading dislocations grown-in from the PbTe buffer layer which produce strain relaxing misfit dislocation segments at the heterointerface. In addition, owing to the local lattice distortions around the misfit dislocation segments, wave-like surface distortions are induced. In the strain relaxation process, the pile-up of misfit dislocations leads to the fomation of multiple step surface elevations, which causes considerable roughening of the epitaxial surface.