Self-assembled InAs quantum dots were grown onto GaAs(100) substrates by using a molecular beam epitaxy technique. The InAs dots were multi-stacked, with 6, 10 or 15 layers within which 2-monolayer thick InAs dot layers and 20-monolayer thick GaAs spacers alternated. Nanostructural features of the multi-stacked layers were characterized by means of scanning transmission electron microscopy. The dots were found to be well-formed vertically with up to 7 layers in each multilayered structure. Stacking faults, so-called volcano-like defects and defects of an asymmetrical down-triangular shape were observed in the 10-layer and 15-layer InAs/GaAs samples. The generation of these defects was explained mainly in terms of the interdiffusion of the group-III atoms. Subsequent strain relaxation, and the gradient of surface chemical potential, were suggested to be the cause of the defects.

Defect Generation in Multi-Stacked InAs Quantum-Dot/GaAs Structures. C.H.Roh, Y.J.Park, K.M.Kim, Y.M.Park, E.K.Kim, K.B.Shim: Journal of Crystal Growth, 2001, 226[1], 1-7