Roder, Melissa
[Author]
;
Danilewsky, Andreas N.
[Degree supervisor];
Wellmann, Peter
[Degree supervisor];
Fiederle, Michael
[Degree supervisor]Albert-Ludwigs-Universität Freiburg Fakultät für Umwelt und Natürliche Ressourcen
Global defect distribution and their influence on the local real structure of 4H-SiC
University thesis:
Dissertation, Universität Freiburg, 2020
Footnote:
Description:
Abstract: In this work 4H-SiC, grown by Physical Vapor Transport (PVT) was investigated with Synchrotron White Beam X-ray Topography (SWXRT) in back-reflection geometry, section topography, X-ray Diffraction Laminography (XDL), polarized light microscopy and at last High Resolution X-ray Diffractometry (HRXRD). Full SWXRT back-reflection wafer-mappings were recorded giving a good dislocation overview. The observed defect features - verified with SWXRT - include threading dislocations like Threading Screw Dislocations (TSDs), superscrews like Micropipes (MPs), dislocation networks in form of Basal Plane Dislocations (BPDs) and Small-Angle-Grain- Boundaries (SAGBs) in different portions. The dislocations are inhomogeneously distributed and show global wafer areas of the same principal dislocation arrangement and density which do not change in growth direction, but there are local defect differences visible within the areas in growth direction. Furthermore, there are features on the topographs which cannot be assigned to the diffraction pattern of a specific dislocation type. They appear as large, shapeless white spot which was assigned to either a void, different polytype, differently oriented grain or an arrangement of closely spaced MPs with the complementary results of polarization microscopy. MPs and other comparable threading dislocations assumed to lie approximately parallel to growth direction [0001] with solely a small but constant inclination arising from an edge component was shown to be incomplete. Polarization microscopy Z-stacks of different MPs reveal strong individual fluctuations of propagation direction and inclination angle in the mm range. XDL showed furthermore a differently pronounced strain field around the MP’s core in accordance to the tilt component. Section topography showed that different dislocation types and densities leading to a local difference of section border bowing and orientation contrast arising Delta Theta extensions. Those differences are in accordance with the different global wafer regions shown in the wafer-mappings. For the real structural analysis, High Resolution X-ray Diffractometry (HRXRD) measurements were performed on several wafer areas representing different dislocation types, densities and their interactions. Bond measurements verified a local lattice parameter difference in dependence of the dislocation content. It turned out that SAGBs show the biggest influence on the lattice parameter in c, whereas MPs leading to the least deviation. Reciprocal Space Maps (RSM) show a difference in the crystal lattice strain and tilt conditions depending not only on the dominant dislocation type but also on the rocking direction along different preferential directions of dislocations. It was shown, that MPs with the least inclination towards growth direction leading to a separation into several strain and tilt segments