Nano-Charakterisierung struktureller und optischer Eigenschaften von Gruppe-Nitrid-Heterostrukturen im Raster-Transmissionselektronenmikroskop (RTEM)- Nano-characterization of structural and optical properties of group-nitride-heterostructures by scanning transmission electron microscopy (STEM)

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The development of new optoelectronic devices using group-III-nitride-heterostructures requires characterization techniques which give spatially resolved information about the local physical and chemical material properties. The goal of this work was the improvement of analytical STEM-techniques and its application on nano-characterization of III-N-heterostructures. The optimization of electron energy-loss spectroscopy provides a measurement techniques which yields spatially resolved information about bandgap energy and dielectric function on a nanometer scale. A combination of STEM-techniques like EELS, convergent electron diffcration (CBED) and Z-contrast imaging was used to characterize and improve structural properties, interfaces and chemical composition of InGaN-layers. The influence of growth parameters on the enhancement of interface sharpness was demonstrated. Additionally nanoscale fluctuations of the In-content could be proved by Z-contrast imaging and quantified by EELS. It was shown how v-defects in InGaN/GaN-superlattices can be eliminated by modulating the growth temperature during epitaxial growth. The improved EELS-techniques were used for measuring optical properties within III-N-heterostructures. The significance of the results could be demonstrated by a comparison to synchrotron measurements and bandstructure calculations. Due to the high spatial resolution optical properties of local separations and defects could be measured and correlated to chemical and structural properties.
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Wissenschaftliche Abschlussarbeiten » Dissertation
Fakultät / Institut:
Fakultät für Ingenieurwissenschaften » Elektrotechnik und Informationstechnik
Dewey Dezimal-Klassifikation:
600 Technik, Medizin, angewandte Wissenschaften » 620 Ingenieurwissenschaften
dielectric function, scanning transmission electron microscope (STEM), heterostructure, GaN, superlattice, InGaN, bandgab, Z-contrast, electron energy-loss spectroscopy (EELS)
Prof. Dr.-Ing Kubalek, Erich [Betreuer(in), Doktorvater]
Prof. Dr. rer. nat. Heime, Klaus [Gutachter(in), Rezensent(in)]
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