Atomic intermixing in short-period InAs/GaSb superlattices

High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and laser-assisted local-electrode atom-probe (LEAP) tomography are utilizing for characterizing short-period InAs/GaSb superlattices with an emphasis on obtaining the atomic concentration profiles with sub-nm resolution. HAADF-STEM permits direct visualization and counting of atomic columns in individual sub-layers. The spatial resolution of HAADF-STEM is sufficient to resolve the anion-cation dumbbells and, on this basis, to follow the atomic distributions across a superlattice. Both methods confirm that InAs-on-GaSb interfaces are wider than GaSb-on-InAs interfaces. The interfacial widths deduced from LEAP tomographic measurements are slightly larger than those extracted from HAADF-STEM micrographs, with the maximum total width not exceeding 4.5 monolayers. LEAP tomographic analysis shows the presence of about 7 at. % of Sb atoms in the middle of the InAs sub-layers, as a result of As/Sb substitutions during growth.