InAs nanowires with AlxGa1−xSb shells for band alignment engineering

InAs nanowires surrounded by AlxGa1−xSb shells exhibit a change in the band alignment from a broken gap for pure GaSb shells to a staggered type II alignment for AlSb. These different band alignments make InAs/AlxGa1−xSb core-shell nanowires ideal candidates for several applications such as TFETs and passivated InAs nanowires. With increasing the Al content in the shell, the axial growth is simultaneously enhanced changing the morphological characteristics of the top region. Nonetheless, for Al contents ranging from 0 to 100 % conformal overgrowth of the InAs nanowires was observed. AlGaSb shells were found to have a uniform composition along the nanowire axis. High Al content shells require an additional passivation with GaSb to prevent complete oxidation of the AlSb. Irrespective of the lattice mismatch being 1.2% between InAs and AlSb, the shell growth was found to be coherent.