Size-controlled quantum dots fabricated by precipitation of epitaxially grown, immiscible semiconductor heterosystems

Epitaxial quantum dots with symmetric and highly faceted shapes are fabricated by thermal annealing of two-dimensional (2D) PbTe epilayers embedded in a CdTe matrix. This novel self-organization scheme is based on the immiscibility of the involved semiconductor materials, which originates from the different bulk bonding configurations and the concomitant lattice-type mismatch. By varying the thickness of the initial 2D layers, the dot size can be controlled in a range between 5 and 25 nm, with areal densities as high as 3 × 1011 cm−2. Control of the quantum dot size allows for photoluminescence tuning over a spectral range between 2.2 and 3.7 µm. Multilayer quantum dot stacks with systematically varying sizes yield ultra-broadband emission, and thus a precondition for the development of superluminescence diodes operating in the near- and mid-infrared.