Evolution of hexagonal lateral ordering in strain-symmetrized PbSe/Pb1-xEuxTe quantum-dot superlattices

Lateral ordering and size homogenization of self-organized PbSe quantum dot s in strain-symmetrized PbSe/PbxEu1-xTe superlattices is studied using atom ic force microscopy. For superlattices with the number of superlattice peri ods varying from N = 1 to 100 it is found that a nearly perfect hexagonal t wo-dimensional (2D) lattice of PbSe dots is formed on the surface already a fter a few periods. A detailed analysis of the dot arrangement shows that w ithin these superlattices, the in-plane spacing of the dots as well as the dot sizes within each PbSe layer remain essentially constant throughout the whole superlattice growth. This marked different behavior as compared to o ther self-assembled quantum dot superlattice systems is explained by the sp ecial ordering mechanism in our material system that is characterized by th e formation of a non-vertical alignment of the PbSe dots in the superlattic e stack due to the very high elastic anisotropy of the IV-VI semiconductors . In addition, from in situ reflection high-energy electron diffraction mea surements it is found that the critical coverage for PbSe islanding, and th us the material distribution between the wetting layer and the islands are not changed within the stack. Therefore, remarkable homogenous three-dimens ionally ordered quantum dot arrays are formed. [S0163-1829(99)02139-6].