Optical characterization of silicon carbide polytypes

A modified experimental scanning laser photoluminescence microscope was used to perform spatially and spectrally resolved measurements on a SIC sample. A scanning grating monochromator integrated into the detection arm of the microscope yielded a high photon collection efficiency at the detector. A cold-finger stage mounted directly onto the X-Y translation stages of the microscope allowed low-temperature PL measurements to be made. One object of the experiment was to test the hypothesis that spectrally and spatially resolved PL could be used to identify different polytypes associated with the grain structure observed in reflected light. Four different regions of the SiC sample were identified and three of these were correlated with low spatial resolution X-ray measurements and found to be polytypes 4H, 6H, and 33R-(alpha)SiC. Room-temperature photoluminescence was used to map the distribution of a deep impurity level and to map crystal defects. Reflected-light measurements were used to map different grain orientations of SiC. The sample was observed to be polycrystalline with most of the grains at the outer edge of the sample.