Cross-sectional HAADF-STEM image, close-view of the cross-section BF TEM, and line scan EDX profile. (a) Cross-sectional HAADF STEM image of the grown GaAs/GaInAs core-MQWs (expected GaInAs shell thickness of 16 nm) surrounded by AlGaAs clads grown on GaAs core and (b) close view of the cross-section BF TEM of the boxed area clearly shows multiple layers including GaAs/GaInAs MQWs and AlGaAs clads. (c) Line scan EDX profile (taken along the white dotted line shown inside the dotted box in Figure 5a) shows GaAs, GaInAs, and AlGaAs shells. The actual GaInAs shell thickness of the 16-nm-thick GaInAs shell was approximately 12 nm. The yellow regions have a higher In composition and represent the GaInAs well layers.