The atomic structure of InAs quantum dots on GaAs(1Â 1Â 2)A

The GaAs(1 1 2)A surface was prepared and InAs QDs were grown on it by molecular beam epitaxy and investigated using in situ scanning tunneling microscopy and reflection high-energy electron diffraction. We confirm and better specify an earlier result that the bare surface is not flat, but is facetted into {2 5 11}A, {1 1 0}, and (1 1 1)A facets forming shallow holes. The InAs wetting layer is not flat, but undulated and disordered, reflecting in part the structure of the bare surface. InAs QDs are formed with high number density typical for coherent QDs, i.e., without any lattice defect at the interface. However, the size distribution is quite broad what is considered to be typical for the A faces of GaAs substrates. From comparison with the literature we conclude on growth of coherent QDs. The shape of the InAs QDs is complementary to that of the holes at the bare surface. The QDs are rather flat entities.