Self-organized low density SiGe quantum dot molecules

Strain feld distribution at the surface of SiGe nanomounds formed by heteroepitaxy is exploited to obtain a positional ordering of the closely spaced Ge quantum dots (quantum dot molecules). We demonstrated, that a low density of the lateral quantum dot molecules (up to 10⁷ cm^-2) can be achieved by tuning of the growth conditions. We present a growth model that provide physical insights into possible mechanisms underlying the formation of lateral SiGe quantum dot molecules. The electronic band structure of the molecules was calculated by 6-band kp method. The results of theoretical study are in a good agreement with experimental measurements of photoluminescence spectra from the samples with quantum dot molecules.