Morphological Changes to InAs Quantum Dots Caused by GaAs Overgrowth

ABSTRACTWe have used in-situ scanning tunneling microscopy (STM) to study the morphological changes to InAs quantum dots (QD's) caused by overgrowth of a GaAs capping layer. We demonstrate that the InAs islands are highly unstable during GaAs overgrowth and that this morphological instability confirms that significant cation intermixing occurs during overgrowth. In particular, the anisotropic nature of the volume redistribution indicates that In surface diffusion is the specific mechanism of In transfer away from the islands. Images taken after 10 monolayers or more of overgrowth reveal that more rapid GaAs overgrowth better preserves the 3D-islands morphology.