X-Ray Diffuse Scattering on Self-Organized Mesoscopic Structures

Abstract

We highlight the great potential of x-ray diffuse scattering for the characterization of mesoscopic structures. The mesoscopic length scale plays a fundamental role at semiconductors, since structures with spatial dimensions in the nanometer regime exhibit quantum size effects. Also the driving forces during epitaxial growth of these structures are most relevant at mesoscopic length scales and they may lead to self-organization processes in that structures can form spontaneously during epitaxial growth. One of the most interesting features are quantum dots (QDs) since they exhibit zero-dimensional electronic properties and thus show an impressive potential for applications in optoelectronic devices. X-ray diffuse scattering is an excellent tool to investigate shape, size, and positional correlation and to characterize the strain field inside and in the vicinity of such self-organized mesoscopic structures. It provides non-destructive structural information over the entire mesoscopic length scale. X-ray scattering is complementary to direct imaging techniques in that it gives a statistical average over large ensembles with high strain sensitivity. The application of different scattering techniques for the structural characterization of mesoscopic structures will be demonstrated. For the example of SiGe islands on Si (001) substrate it will be shown that x-ray diffuse scattering is able to reveal details of germanium distribution in such islands. In a second example the investigation of the asymmetric shape and size of InP QDs that are grown on (001) In0.48Ga0.52 P/GaAs is described. The influence of positional correlation on the diffuse scattering will be discussed.