Interdiffusion and surface segregation in stacked self-assembled InAs/GaAs quantum dots

We have investigated interdiffusion and surface segregation in molecular-beam-epitaxially-grown stacked self-assembled InAs/GaAs quantum dots. Using high-resolution cross-sectional scanning tunneling microscopy, we observe lateral variations in the vertical positions of In atoms in both the wetting layers and dot stacks. In some regions, the wetting layer thickness is much less than the dot height, while in other regions, the dot is immersed in the wetting layer. Using In and Ga atom counting, we obtain vertical In-Ga interdiffusion and 1/e segregation lengths of 1.25 and 2.8 nm, respectively. In the dot stacks, significant In-Ga intermixing, primarily due to In surface segregation, is apparent. (C) 1999 American Institute of Physics. [S0003- 6951(99)04244-8].