Characterization of deep levels in SiC by photoluminescence spectroscopy and mapping

Deep-level photoluminescence (PL) was investigated in 4H-SiC wafers under the below bandgap excitation. The excitation with a photon energy of 2.54 eV induced not only well-defined vanadium-related lines but sharp lines and an intense band in the range between 1.0 and 1.4 eV, which were very weak under the above bandgap excitation and were not reported previously. Microscopic mappings of these emissions revealed that their intensities increased around macrodefects such as cracks and hexagonal defects, although their intensity patterns were substantially different. We suggest that the gettering effect of the macrodefects is responsible for the microscopic intensity variations: Impurities and point defects participating in the deep-level PL processes are drawn towards the macrodefects by the strain field.