Fabrication of Axial and Radial Heterostructures for Semiconductor Nanowires by Using Selective-Area Metal-Organic Vapor-Phase Epitaxy

Figure 10

GaAs QW width calculated from PL spectra and growth rate and analysis by TEM. (a) Comparison of GaAs QW width obtained from PL peak energy with that estimated from axial growth rate of GaAs NW. NW pitch was 1 μm. Inset in upper right is dark-field STEM image of heterostructure NW taken with electron-beam direction parallel to ⟨−110⟩. Inset at left above has depth profile of Al composition measured from top of NW by using EDX, which indicates GaAs QW portion sandwiched by AlGaAs. White broken line along ⟨111⟩ direction on STEM image indicates path scanned by electron beam for EDX. (b) Bright-field STEM image of NW. (c) Transmission electron diffraction pattern. (d) High-resolution TEM image of NW top portion indicated by white rectangle on STEM image of (b). Twin boundaries are indicated by arrows. (e) Dark-field STEM image of (b). Layer positions of GaAs QW and AlGaAs barriers estimated along ⟨111⟩ direction are indicated by broken arrows [30].