Definition of a problem: low angle grain boundaries in SiC boules

The high resolution x-ray diffraction on good quality Lely platelets exhibits one narrow peak in rocking curve scans with the FWHM of between 10 and 20 arc seconds. The scan on PVT wafer frequently is much broader and can be composed of multiple peaks. An example of two such scans is shown in Fig. 1 below (from Glass et al. J. Cryst. Growth 132 504 (1993)).

Fig. 1 High resolution x-ray diffraction (0006) w scans on Lely platelet and a wafer grown by PVT.

The presence of multiple narrow peaks in x-ray reflection was interpreted as due to slight misorientations between different regions in PVT crystals. The entire boule is thought of as composed of highly perfect domains with typical size in millimeter range separated from each other by domain walls with high defect densities. A brief inspection of the etched SiC wafer surface shows that the etch pits frequently form complex patterns of lines possibly corresponding to domain walls. Frequently, domain walls are referred to as low angle grain boundaries.

However, although the domain structure of SiC was discovered almost a decade ago, the quantitative measurements of domain misorientations, the domain morphology, and the mechanisms which are responsible for their formation remain elusive. One type of domain structure frequently found in high quality SiC wafers is described in Pure tilt boundaries around c-axis .

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