"Highly luminescent nanocrystal quantum dots fabricated by lattice-type mismatched epitaxy",
W. Heiss, E. Kaufmann, M. Boeberl, T. Schwarzl, G. Springholz, G. Hesser, F. Schaeffler, K. Koike, H. Harada, M. Yano, R. Leitsmann, L.E. Ramos, F. Bechstedt,
Physica E 35, 241 (2006),

Lattice-type mismatched heteroepitaxy is demonstrated as a novel concept for the fabrication of almost-ideal highly-luminescent nanocrystal quantum dots that are coherently embedded in a single-crystalline matrix. In this approach, the formation of quantum dots is induced by transformation of a metastable epitaxial 2D quantum well into an array of isolated nanocrystals with highly symmetric shape. This process is driven by the lattice-type mismatch between the constituent materials and the resulting miscibility gap. The investigated PbTe/CdTe hererosystem has a model character because it combines two compounds with different cubic lattice types but almost identical lattice constants. The obtained epitaxial nanocrystals exhibit outstanding properties such as a well-defined symmetric shape, the absence of strain, intermixing and a wetting layer, which is in contrast to the conventional Stranski-Krastanow quantum dots. The small-rhomboedric-cubo-octahedron PbTe/CdTe nanocrystals on GaAs substrates display intense room temperature mid-infrared luminescence as is crucial for device applications. Ab initio density-functional theory is used to clarify the interface structure, indicating that the covalent and ionic bonding character of CdTe and PbTe is maintained across the interface.