A method to tune the island size and improve the uniformity for the in situ formation of InGaAs quantum dots on GaAs

The use of island formation during the epitaxy of InxGa1−xAs on GaAs can be applied to the in situ formation of quantum dots. Adjusting the alloy composition toward a larger degree of cation disorder (Ga and In intermixing) can decrease the island size and improve the island uniformity simultaneously. Under the same deposition conditions with a thickness of 15 monolayers, the dot size can be tuned from 125 × 100 to 30 × 28 nm2 in lateral dimensions as the In composition changes from 1 to 0.5. Among all conditions, In0.5Ga0.5As dots show a high density of 5 × 1010 cm−2 and exhibit the best uniformity. These small-sized and dislocation-free islands are of interest for the formation of high-quality quantum dots.