Atomic Ordering in Self-assembled Epitaxial II-VI and IV-VI Compound Semiconductor Quantum Dot Systems

Transmission electron microcopy (TEM) in both the parallel illumination and scanning probe mode revealed atomically ordered entities within a 5 to 250 nm range in a IV-VI and a II-VI compound semiconductor quantum dot (QD) system. While the II-VI system was a nominal [001] CdSe/(Mn0.1Zn0.9)Se multilayer structure with the QDs embedded, the IV-VI system nominally consisted of [111] PbSe islands. The comparison of photoluminescence (PL) spectra from the CdSe/(Mn0.1Zn0.9)Se structure with those of a reference structure, that was grown to the same nominal specification under otherwise identical conditions except that no Mn was incorporated into the cladding layers, revealed for the former sample two peaks at approximately 2 and 2.1 eV. We tentatively attribute these two PL peaks to two groups of atomically ordered entities.