Mechanisms and Anomalies in The Formation of Inas—Gaas(001) Quantum Dot Structures

We examine critically the available information, both experimental and theoretical, on the formation of self-assembled quantum dots (QDs) in the lattice-mismatched InAs/GaAs system via a presumed Stran- ski-Krastanov growth mode. We consider the orientation and reconstruction specificity of QD formation, the structure and composition of the wetting layer, which appears to be a necessary precursor to QDs, and by drawing an analogy with homoepitaxy on GaAs(001)—β2(2x4), we argue that the surface structure prior to dot formation is an essential factor for the comprehensive understanding of this phenomenon. The shape of QDs is important in the evaluation of their electronic structure and we indicate how errors in the interpretation of diffraction-based techniques have resulted in the dots being ascribed regular crystallographic features in the form of low index facets, whereas they have rather irregular shapes and curved surfaces. Finally we discuss compositional measurements of mass transport effects that occur during encapsulation of the QDs with a layer of GaAs, used to provide electronic confinement.