In-situ X-ray diffraction study on structural evolution of InAs islands on GaAs(001) during annealing

Takahashi, Masamitsu; Kaizu, Toshiyuki; Mizuki, Junichiro

Stranski-Krastanov islands are far from equilibrium and coarsening occurs when they are annealed. This coarsening is driven by chemical potential differences between islands. In lattice-mismatched systems, the chemical potential difference is governed by strain as well as surface and interface energies. In the present work, we discuss ripening kinetics of InAs/GaAs(001) on the basis of in situ X-ray diffraction, which is sensitive to strain distribution within islands. Experiments were performed at a synchrotron beamline 11XU at SPring-8 using an X-ray diffractometer integrated with an MBE chamber. From X-ray diffraction data, the lattice constant distribution and the height of the InAs quantum dots were evaluated during growth and annealing at substrate temperatures ranging from 430C to 480C. X-ray results suggest that strain relief via thermally enhanced alloying plays a major role in the coarsening process as it does in continuous growth of InAs.