INTERMIXING AND SHAPE CHANGES DURING THE FORMATION OF INAS SELF-ASSEMBLED QUANTUM DOTS

The initial stages of GaAs overgrowth over self-assembled coherently s trained InAs quantum dots (QDs) are studied. For small GaAs coverages (below 5 nm), atomic force microscopy (AFM) images show partially cove red island structures with a regular size distribution which are elong ated in the [011] direction. Analysis of the AFM profiles show that a large anisotropic redistribution of the island material is taking plac e during the initial GaAs overgrowth. Short time annealing experiments together with photoluminescence spectroscopy on annealed QDs are cons istent with a Ga and In intermixing during the overgrowth. Surface QDs capped with 5 nm or more GaAs show a strong luminescence intensity in dicating that surface QDs are remarkably insensitive to surface recomb ination effects. (C) 1997 American Institute of Physics.