On the origin of threading dislocations during epitaxial growth of III-Sb on Si(001): A comprehensive transmission electron tomography and microscopy study

Electron tomography and complementary (scanning) transmission electron microscopy (STEM) are applied to investigate the origin of threading dislocations in the large lattice misfit, heteroepitaxial system of III-Sb on vicinal Si(001). Buried AlSb islands of the initial wetting layer are revealed at the interface toward the substrate in the three-dimensionally reconstructed data. Locations of island coalescence are retrieved from the tomogram. Complementary (S)TEM measurements reveal the location of threading dislocations and the presence of antiphase boundaries at the same specimen area. The number density of threading dislocations emanating from the interface and their distribution are unexpected. It is shown that the presence of threading dislocations is not simply correlated to sites of AlSb-islands coalescence or to the film closure during the transition from a 3D to a 2D growth. Moreover, an interaction with antiphase boundaries is suggested by the presented observations. Consequently, the contemporary notion of threading dislocation formation is refined and, eventually, it is suggested that measures to avoid antiphase domains and such to reduce threading dislocations have to be balanced for future strategies to epitaxially grow sphalerite structure III-V semiconductors on Si or Ge.