Cooperative nucleation and evolution in InGaAs quantum dots in multiply stacked structures

We report a type of vertical self-organization of In0.6Ga0.4As quantum dots (QDs) wherein the dot density for the top layer (N-T) doubles that of the seed layer (N-S). The experimental observation fits well with a scheme of Q D vertical self-organization accompanied by additional cooperative dot nucl eation at the face centers of an approximate two-dimensional array defined by the embedded seed dots. The dots in the top layer undergo a shape transi tion from {023} to {011} and a simultaneous shape stabilization and size eq ualization. (C) 2001 American Institute of Physics.