Simulation of Grazing-Incidence Synchrotron White Beam X-ray Topographic Images of Micropipes in 4H-SiC and Determination of Their Dislocation Senses

Abstract

Detailed comparison has been drawn between synchrotron white beam X-ray topographic images of micropipes in 4H-SiC, recorded using pyramidal plane reflections in grazing-incidence geometry, and images simulated using the ray-tracing method. The simulations were carried out with and without the influence of surface relaxation effects. The images simulated in the absence of surface relaxation effects appear as white elliptical shaped features, canted to one side or other of the g-vector (depending on the dislocation sense), surrounded by a dark contrast perimeter which thickens at both ends of the major axis and which exhibits two fold symmetry axes parallel to the major and minor axes. On the other hand, on the images simulated taking into account the effects of surface relaxation, the features are again canted to one side or other of the g-vector (depending on the dislocation sense) but do not exhibit the same symmetry in that one of the sides of the oval shape is flattened (along the major axis) and the distribution of intensity around the perimeter no longer possesses the two fold symmetry axes parallel to the major and minor axes. While the details of the distribution of the dark perimeter contrast observed on the recorded images are not so easy to correlate with the simulated distributions, the sense of cant of the roughly elliptical white features on the observed images can be easily correlated with the simulations. Since the sense of cant has the same behavior as a function of dislocation sense for simulations carried out with and without surface relaxation, this provides a high level of confidence that the sense of cant of these features can be readily used to determine the senses of the micropipes.

Direct Determination of Burgers Vectors of Threading Mixed Dislocations in 4H-SiC Grown by PVT Method

“…This simulation tool was developed in our group and has been useful in predicting contrast for various defects in single crystals and has also helped in understanding crystalline defects. [8][9][10] …”

Micropipe Reactions in Bulk SiC Growth

“…The combination of synchrotron x-ray topography and optical microscopy succeeded in shedding light on the elucidation of the origin and transformation of dislocations and stacking faults (Tsuchida et al, 2007). The highly coherent beams allowed to analyze dislocation types and structures (Nakamura et al, 2007;Wierzchowski et al, 2007), the Burgers vectors senses and magnitudes (Chen et al, 2008;Nakamura et al, 2008), and the propagation and distribution of threading dislocations (Kamata et al, 2009) …”

SR phase contrast imaging to address the evolution of defects during SiC growth

“…Nowadays, dislocation processes in SiC crystals of low dislocation density are studied by means of synchrotron radiation (SR) X‐ray topography 9, 10. The emphasis in our study is on the transformation of defects starting from the beginning of growth where many defects cause mosaic spread.…”