Centrosymmetric PbTe/CdTe quantum dots coherently embedded by epitaxial   precipitation
  A concept for the fabrication of highly symmetric quantum dots that are coherently embedded in a single crystalline matrix is demonstrated. In this approach, the formation of the quantum dots is induced by a transformation of an epitaxial 2D quantum well into an array of isolated precipitates with dimensions of about 25 nm. The formation process is driven by the immiscibility of the constituent materials resulting from their different lattice structures. The investigated PbTe/CdTe heterosystem combines two different cubic lattices with almost identical lattice constants. Therefore, the precipitated quantum dots are almost strain free and near thermodynamic equilibrium they exhibit the shape of small-rhombo-cubo-octahedrons. The PbTe/CdTe quantum dots, grown on GaAs substrates, display intense room temperature luminescence at wavelength around 3.2 micrometer, which makes them auspicious for applications in mid-infrared photonic devices. 
W. Heiss, H. Groiss, E. Kaufmann, G. Hesser, M. Boberl, G. Springholz,   F. Schaffler, K. Koike, H. Harada, and M. Yano