The improvement of growth techniques in the characterization of semiconductor nanostructures, has recently resulted in the realization of quasi-zero dimensional semi-conducting devices (quantum dots) of excellent performances and of reproducible quality (1,2). The design and fabrication of these devices strongly depends on the ability to control parameters that influence the quantum confinement namely the shape, dimension and size distribution of the dots. High spatial resolution structural and analytical techniques are crucial to obtain nanoscale information about the shape of the dots, the structural and chemical abruptness of the interfaces, and the composition of the dots (3).

In this paper we show the results of a structural and chemical characterization of In0.5Ga0.5As/GaAs quantum dots grown by low-pressure metal organic chemical vapor deposition (LP-MOCVD) on a (100) GaAs substrate. The growth was performed in a horizontal LP-MOCVD system (AIXTRON 200 AIX).