Self-assembly of heterojunction quantum dots

The fabrication of a self-assembled heterojunction quantum dot structure composed of multiple materials is reported. This structure consists of a composite dot formed of an initial core of one material which results from normal self-assembly, followed by the epitaxy of a crown composed of a similarly strained material. Finally the entire dot structure is capped with a barrier material closely lattice matched to the substrate. In this demonstration, self-assembled InAs quantum dots were first formed on a GaAs substrate and subsequently crowned with GaSb. The entire structure was encapsulated with a GaAs cap layer. Atomic force microscopy shows that additional nucleation between the InAs layers has been minimized and cross-sectional transmission electron microscopy shows the formation of the composite structure. (c) 2006 American Institute of Physics.