Effect of dissimilar anion annealing on structures of InAs/GaAs quantum dots

In this paper, we report microstructural characterization of InAs/GaAs quantum dots grown by molecular beam epitaxy. The InAs islands were annealed in a range of temperatures under Pa flux. Prior to annealing, it is shown that the InAs islands are mainly lens-shaped, mostly vertically self-aligned and coherent to GaAs (10 0) substrate. Relaxation by misfit dislocations is occasionally found. Abnormal relaxation is observed in larger islands. Stacking faults in a V-shape are frequently formed in the lateral sides of these regions. No obvious change in island density and self-alignment occurred when the dots are annealed under Pa flux at 300degreesC. In contrast, remarkable changes took place upon annealing at 350degreesC. The vertically self-aligned islands disappear, and smooth interfaces were obtained. This morphological transition is argued to result from the replacement of arsenic by phosphorus in the InAs dots. The damage to the crystalinity of the abnormally relaxed regions cannot be removed by the post-growth annealing. The remarkable morphological transition by post-growth annealing under dissimilar anion atmosphere offers another possibility for tuning the dot morphology and hence their electronic properties. (C) 2003 Elsevier Science B.V. All rights reserved.