Optimizing the growth procedure for InAs quantum dot stacks by optical in situ techniques

The influence of the GaAs cap layer thickness on the surface morphology and stoichiometry of InAs quantum dot (QD) layers grown on GaAs(001) was inves tigated by real-time reflectance anisotropy spectroscopy (RAS) and ellipsom etry. A redistribution of InAs from partially covered islands to the surfac e of the GaAs cap layer was found, Introducing a well-defined growth interr uption (GRI) during cap layer growth, a narrower size distribution of the I nAs islands could be achieved and, moreover, large clusters and dislocation s in the sample could be completely avoided. Transmission electron microsco pical images of stacked QD layers substantiate the growth model of island r edistribution by showing a fractional second wetting layer. Using this proc edure of island redistribution dislocation free 5-fold InAs QD stacks were realized. (C) 2000 Elsevier Science B.V. All rights reserved.