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

Initial stages of self-assembled growth of InAs dots on GaAs(001) and a pos tgrowth evolution of the deposited surface have been investigated by reflec tance-difference (RD) spectroscopy and reflection high-energy electron diff raction (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 dim er along the [110] direction of the c(4 x 4) As-rich GaAs(001) surface beco mes dimerized along the [-110] direction. Postgrowth behavior has been stud ied at 480 degrees C after 1.9-ML deposition of InAs. During postgrowth, th e As-dimer-related RD signal returns to signals observed at lower InAs depo sition. This behavior gives evidence that the InAs coverage is reduced by p ostgrowth. Furthermore, positive offsets that increase in amplitude with ph oton energy appear in the RD spectra of the postgrown samples. (C) 2000 Els evier Science B.V. All rights reserved.