Indium segregation during multilayer InAs/GaAs(0Â 0Â 1) quantum dot formation

Indium segregation during the growth of multilayer InAs/GaAs(0 0 1) quantum dot (QD) structures has been studied using reflection high-energy electron diffraction (RHEED) measurements of the critical coverage (θcrit) for second layer QD formation. A model bilayer structure was used in order to separate the effects of segregation and strain. The structure comprises an upper QD layer formed on top of a buried two-dimensional InAs layer. Growth temperature and the GaAs spacer layer thickness (S) are both found to have a significant effect on θcrit. Indium segregation during growth of the capping layer leads to the presence of a surface In adatom population prior to deposition of the second InAs layer. Segregation occurs for S up to 8 nm at 510 °C, this value being reduced by ∼50% at 450 °C.