Surface compositional gradients of InAs/GaAs quantum dots

With laterally resolved photoemission spectroscopy, we obtained In and Ga surface concentration maps of InAs/GaAs quantum dots. Our data demonstrate that the dot composition is neither pure InAs nor homogeneous InxGa1-xAs, but presents an In concentration increasing from the borders to the center of the dots. Besides, our observations suggest strong In segregation (x similar to 0.9) on the surface of the dots and of the surrounding wetting layer. Such segregation, well known for two-dimensional InAs/GaAs growth, had not been directly observed so far on the dots, and should be taken into account to model size and composition of GaAs-overgrown structures. (c) 2005 American Institute of Physics.