The ability to control and reproduce during the growth process the structural properties of semiconductor nanostructures and especially self-assembled Stranski Krastanov quantum dots is critical to the performance of many advanced semiconductor devices. Ex-situ analytical tools like AFM, STM, TEM and grazing incidence x-ray diffraction have been shown as being extremely valuable in extracting important information pertaining the density, the shape and size of fabricated dots. Unfortunately their integration in growth vessels for during growth in-situ analyses remains cost-prohibitive/challenging and requires non-optimal growth geometries that makes them marginally applicable for real-time assessment of to the evolution of SKQDs during standard fabrication processes. Until recently, the evaluation of quantum dots by reflection high-energy electron diffraction (RHEED), available as standard non-intrusive and in-situ diagnosis tool on common high vacuum epitaxy systems (i.e. MBE, CBE, LPVPE,), has been mostly limited to “qualitative surveys”. However recent developments and systematic work on modeling (atomistic strain + diffraction theory) and experimental analyses of the intensity distributions in RHEED patterns of quantum dots demonstrates possibilities for “quantitative analysis”. Within this framework the presentation will provide an overview of these developments. A particular emphasis is given to the applicability of RHEED for a real-time extraction of average size (height) and shape of dots and the evolution of these microscopic parameters during the epitaxial growth process of InAs self-assembled quantum dots on GaAs.
Photovoltaic’s and Nanostructures Laboratory, Center for Advanced Materials, University of Houston