In segregation effects during quantum dot and quantum ring formation on GaAs(001)

In segregation during InAs growth on GaAs(001) is studied using a real time, in situ technique capable of measuring sample accumulated stress. A 50% surface In segregation of liquid-like stress free matter is deduced. A picture of growth below critical thickness for quantum dot formation is discussed on the basis of the equilibrium between pseudomorphic InAs and liquid In dominated by the stress energy. Quantum rings are produced when large (>10 nm height) quantum dots are covered with 2 nm of GaAs cap. A formation mechanism of the rings is presented. The possibility of tailoring photoluminescence emission through control over size and shape is demonstrated.