InAs quantum dot evolution observed by in-situ scanning tunneling microscopy during molecular beam epitaxy growth

We have successfully investigated the self-assembly mechanism for InAs quantum dots (QDs) formed on GaAs(001) by using a unique scanning tunnelling microscope (STM) placed within the molecular beam epitaxy (MBE) growth chamber. The images elucidate the mechanism of QD nucleation, demonstrating directly that not all deposited In is initially incorporated into the lattice, hence providing a large supply of material to rapidly form QDs via islands containing tens of atoms. kinetic Monte Carlo (kMC) simulations based on first-principles calculations show that tiny alloy fluctuations, like atomistic point defects, in the InGaAs wetting layer prior to are crucial in determining nucleation sites.