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Synchrotron topographic investigation of SiC bulk crystals and epitaxial layers
|Wojciech Wierzchowski 1, Krzysztof Wieteska 2, Walter Graeff 3|
1. Institute of Electronic Materials Technology (ITME), Wólczyńska 133, Warszawa 01-919, Poland
X-Ray diffraction topographic methods exploring synchrotron source of X-Ray were applied for studying different monopolytipic 6H and 4H SiC crystals and SiC homoepitaxial layers. A set of investigated samples included the crystals and epitaxial layers of a very good crystallographic perfection, with reduced number of micro-pipes and with low concentration of dislocations. Some of the samples were cut out along the [00×1] growth axis of a 6H SiC boule.
The synchrotron topographic methods included both those exploring white and monochromatic beam of 0.111 nm wavelength. The monochromatic beam topographs were completed by recording of local diffraction curves using the 50mm ´50 mm spot beam.
The synchrotron topographic methods provided valuable information both in the case of higher and low density of defects in crystals. In the first case particularly useful results were obtained using back-reflection white beam synchrotron section topography, which reproduced the images from a large thickness of the samples intersected by the beam. The section topographs revealed a great part of macro and micro-pipes present in the samples, reproduced as white areas, similarly as hexagonal voids formed in some crystals.
The additional possibility offered exposing the white beam topographs through a fine mesh with the distance between the wires equal to 0.7mm, which was very useful in revealing and evaluation of the lattice deformation. Thanks to low attenuation of radiation in SiC crystals very good results were obtained using a mesh also in case of Bragg-case section topography.
It was possible to reveal some interesting cases of lattice deformation in the investigated crystals. In particular a structure of oval grains with the disorientation of some minutes was observed in some samples cut out perpendicular to [00×1] growth axis, while in samples cut out along growth axis the characteristic misoriented stripes were revealed.
It was possible to obtain well resolved dislocations images in crystals of good quality with the use of all considered synchrotron topographic methods. The Bragg-case monochromatic beam topographs and white beam section topographs provided the images of dislocation enabling the numerical simulation of the images. It was possible to confirm the dominant screw-type character of observed dislocations.
Presentation: Invited oral at Joint Fith International Conference on Solid State Crystals & Eighth Polish Conference on Crystal Growth, Polish-Japanese-German Crystal Growth Meeting, by Wojciech Wierzchowski
See On-line Journal of Joint Fith International Conference on Solid State Crystals & Eighth Polish Conference on Crystal Growth
Submitted: 2007-01-24 00:12 Revised: 2009-06-07 00:44