Growth modes and interfaces of InGaN nanostructures by planar and cross-sectional STM

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This project aims at a detailed understanding of the growth modes and growth mechanisms which are important for the assembly and quality of group-III-nitride based quantum structures. For a detailed structural characterization in-situ scanning tunneling microscopy studies during growth will be used to achieve information regarding the growth modes of this material system, segregation effects, the origin of compositional fluctuations in InGaN quantum well structures, and the nucleation of quantum dots as well as their dependence on the growth parameters. The in-situ experiments will be complemented by ex-situ investigations using grazing incidence x-ray diffraction and small angle scattering, transmission electron microscopy, synchrotron radiation based x-ray diffraction and scattering, and ex-situ STM. This combination of analytical tools will allow us to study a wide variety of structural parameters and their distribution, like surface morphology, size and shape of quantum dots, and ordering of the lateral and/or vertical arrangement of quantum structures. Samples for this project will be provided by the growth resources applied for in project I-1. The results obtained from the experiments to be performed in this project may, on the one hand, be used to understand growth and enable reliable predictions on the impact of growth parameters in close cooperation with project III-1. On the other hand, the results of this project will be essential to establish growth parameters suitable for an optimized fabrication of quantum dot arrays as needed for projects I-1 and I-2. In addition, the knowledge of structural parameters is essential for a theoretical description of the electronic and optical properties of such quantum structures. Therefore the presently proposed project can provide valuable input parameters for the projects III-2 and III-3. The issue of the impact of surface dopant coverage on the growth mode will be addressed in close cooperation with II-2.