Self-assembled growth of InAs-quantum dots and postgrowth behavior studied by reflectance-difference spectroscopy

Initial stages of self-assembled growth of InAs dots on GaAs 001.and a postgrowth evolution of the deposited surface have been investigated by reflectance-difference RD.spectroscopy and reflection high-energy electron diffraction RHEED.. A significant change in the RD spectrum occurs even at 0.1-monolayer ML.deposition of InAs. With increasing InAs deposition, the As-dimer-elated RD sign is inverted, which indicates that the original As dimer along thew110xdirection of the c 4=4.As-rich GaAs 001.surface becomes dimerized along thewy110xdirection. Postgrowth behavior has been studied at 4808C after 1.9-ML deposition of InAs. During postgrowth, the As-dimer-related RD signal returns to signals observed at lower InAs deposition. This behavior gives evidence that the InAs coverage is reduced by postgrowth. Furthermore, positive offsets that increase in amplitude with photon energy appear in the RD spectra of the postgrown samples. q2000 Elsevier Science B.V. All rights reserved.