Investigation of reflection anisotropy induced by micropipe defects on the surface of a 4H-SiC single crystal using scanning anisotropy microscopy

Optical reflection anisotropy microscopy mappings of micropipe defects on the surface of a 4H-SiC single crystal are studied by the scanning anisotropy microscopy (SAM) system. The reflection anisotropy (RA) image with a 'butterfly pattern' is obtained around the micropipes by SAM. The RA image of the edge dislocations is theoretically simulated based on dislocation theory and the photoelastic principle. By comparing with the Raman spectrum, it is verified that the micropipes consist of edge dislocations. The different patterns of the RA images are due to the different orientations of the Burgers vectors. Besides, the strain distribution of the micropipes is also deduced. One can identify the dislocation type, the direction of the Burgers vector and the optical anisotropy from the RA image by using SAM. Therefore, SAM is an ideal tool to measure the optical anisotropy induced by the strain field around a defect.