Atomic structure and strain of the InAs wetting layer growing on GaAs(001)-c(4 X 4)

Using scanning tunneling microscopy, the authors studied the wetting layer evolution of InAs on GaAs(001)-c(4 X 4) and unraveled the different surface reconstructions during this process. At low coverages the deposited InAs material is first stored at defects and then at the hollow sites of the GaAs(001)-c(4 X 4) reconstruction. Close to an InAs coverage of 2/3 monolayer (ML), the whole surface abruptly reconstructs into an In2/3Ga1/3As monolayer, showing mainly a (4 X 3) reconstruction. Further deposited InAs is arranged in three different InAs(001)-(2 X 4) reconstructions on top of the In2/3Ga1/3As layer. After quantum dot occurrence above about 1.4 ML of InAs, a material transport away from the wetting layer is observed by a partial reappearance of the underlying (4 X 3) reconstruction. A detailed analysis of the observed reconstructions clearly shows that their specific atomic arrangements lead to a reduction of strain, while increased amounts of strain at the wetting layer start to build up above about 1.4 ML of deposited InAs, thus leading to quantum dot formation. (C) 2010 American Vacuum Society. [DOI:10.1116/1.3456169]