Effects of a Si molecular beam on the formation of InAs quantum dots

We have investigated the effect of a Si molecular beam on self-assembled InAs quantum dots (QDs) on GaAs grown by molecular beam epitaxy. We changed the Si coverage (Θ) and the substrate temperature and monitored their effects on the InAs QDs by using atomic force microscopy. The 2D-3D transition of self-assembled InAs QDs was found to be delayed by the existence of Si-adatoms. As the Si coverage (Θ) increased, the density of QDs increased, but after a critical Si coverage (Θ=0.12), the density decreased rapidly due to the coalescence of dots. This indicates that Si atoms act as nucleation centers for the formation of self-assembled InAs QDs. By optimizing the Si coverage (Θ) and the substrate temperature, we could obtain InAs QDs with high density.