The effects of rapid thermal annealing on InGaAs quantum dots grown by atomic layer molecular beam epitaxy to the structural transformation and optical properties are investigated. No misfit dislocation was observed from either the as-grown or annealed dots. The size and composition of the quantum dots become more uniform upon annealing mainly from the height fluctuation as predicted by the theoretical model. Large bandgap blue shifts, resulted from the In and Ga interdiffusion, were observed with the preservation of three-dimensional carrier confinement. The GaAs/AlGaAs superlattice was found to minimize the defect diffusion and dot interdiffusion during the high-temperature epitaxial overgrowth. (c) 2006 Elsevier B.V. All rights reserved.