Fabrication of Axial and Radial Heterostructures for Semiconductor Nanowires by Using Selective-Area Metal-Organic Vapor-Phase Epitaxy
Figure 7
SEM images of NWs and changes in NW height and diameter. NW pitch μm and SiO2 mask opening size nm. (a), (b), and (c) correspond to SEM images for GaAs NWs, core-shell NWs, and heterostructure NWs. White dotted parallel lines bridged between SEM images (a) and (b), or (b) and (c) clarify how NW height changed between growth steps. (d) Changes in height and diameter of NWs corresponding to growth steps of GaAs NW (GaAs core growth time: 5 min), GaAs/AlGaAs core-shell NW (AlGaAs shell growth time: 2.5 min), and GaAs/AlGaAs/GaAs heterostructure NW (top GaAs growth time: 2 min). (e) and (f) illustrate reduced NW diameter by introducing GaAs core. (g) and (h) are SEM images of NW grown with and without GaAs core, corresponding to schematics in (e) and (f). Growth time for AlGaAs is 20 min and 5 min for GaAs for structures in (f) and (h) [30].
