Structural defects in SiC ingots investigated by synchrotron diffraction imaging

4H silicon carbide as-grown ingots were investigated by diffraction imaging using synchrotron radiation. The white beam section topographs obtained for various sample geometries allowed us to reveal structural imperfections before slicing the bulky ingots to the thin wafers used as electronic device substrates. The systematic investigation indicated that the observed inclusions of different polytypes in 4H-SiC ingots are correlated with the 8° off-axis orientation of the seed. These inclusions, formed at the beginning of the crystal growth, provoke planar defects that propagate along the main vertical axis of the cylindrical crystal. New findings permitted us to understand the inclusion formation with the aim to increase the useful volume.

Source:IOPscience

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Evaluation of Model for Determining Nitrogen Doping Concentration from Resultant Strain in Heavily Doped 4H-SiC Crystals

Significant strain in 4H-SiC substrates can be introduced by impurity incorporation in heavily doped 4H-SiC crystals. The non-destructive X-ray double-crystal contour mapping method we reported recently is a powerful tool to estimate the lattice strain levels in 4H-SiC substrates with different doping concentrations. The lattice strain maps were derived from 11-20, 1-100 and 0008 reflections. Result shows that lattice strains within the basal plane and along the [0001] direction are in the order of 10-3 and 10-4 respectively. Hall effect measurements performed to determine the doping concentration of 4H-SiC substrates show an increase in doping concentration with the decrease of contact resistivity. X-ray rocking curve measurements were employed to confirm the existence of significant lattice distortion in heavily doped 4H-SiC substrates, which is in good agreement with the lattice strain analysis based on X-ray contour mapping method.

Source:IOPscience

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