Transmission-electron microscopy study of the shape of buried InxGa1-xAs/GaAs quantum dots

High-resolution electron microscopy, on-zone bright-field imaging, and image simulation were used to investigate the shape of capped In0.06Ga0.4As/GaAs semiconductor quantum dots. Cross-section [110] high-resolution images suggest that the quantum dots are lens shaped, while the [001] on-zone bright-field images show a contrast that suggests a quantum dot morphology with four edges parallel to [100]. The image simulation, however, suggests that a spherical quantum dot can produce a square-shaped image. These observations lead to the conclusion that the quantum dots in buried In0.6Ga0.4As/GaAs semiconductor heterostructures are lens shaped.