The effect of GaAs cap layer thickness upon the surface morphology and stoichiometry of InAs quantum-dot layers, grown onto GaAs(001), was investigated by means of real-time reflectance anisotropy spectroscopy and ellipsometry. Redistribution of InAs, from partially covered islands to the surface of the GaAs cap layer, was found. By introducing a well-defined growth interruption during cap layer growth, a narrower size distribution of the InAs islands could be obtained and large clusters and dislocations in the sample could be completely avoided. Transmission electron microscopic images of stacked quantum-dot layers supported the growth model, for island redistribution, by revealing a fractional second wetting layer. By using this island redistribution procedure, dislocation-free 5-fold InAs quantum-dot stacks were obtained.

Optimizing the Growth Procedure for InAs Quantum Dot Stacks by Optical in situ Techniques. E.Steimetz, T.Wehnert, H.Kirmse, F.Poser, J.T.Zettler, W.Neumann, W.Richter: Journal of Crystal Growth, 2000, 221, 592-8