Synchrotron X-ray topographic characterization of dislocations in 6H-SiC axial samples

Abstract

Wide bandgap semiconductor, 6H-SiC, is being applied in photoconductive semiconductor switches (PCSS) due to its semi-insulating properties. The behavior of the dislocations in 6H- SiC under the application of voltage and laser in such devices is of particular interest. In this study, synchrotron X-ray transmission topography, grazing incidence topography and rocking curve topography are applied to characterize the types and distribution of defects in (1 1 –2 0) oriented wafers. Threading edge dislocations (TED), threading screw dislocations (TSD), threading mixed dislocation (TMD) and basal plane dislocations (BPD) in 6H-SiC axial samples are revealed in the X-ray topographs. TEDs are observed to be more likely off c-axis compared to TSDs/TMDs. Contrast features of BPDs differ depending on their Burgers vectors and orientation with respect to wafer surface on rocking curve topographs and grazing incidence topographs. Applying ray tracing simulations, the configurations of BPDs can be determined, and the threading dislocations (TED, TSD and TMD) can be distinguished in grazing incidence topographs. The understanding of the nature and the distribution of these dislocations will help predict their propagation and movement under the application of voltage and laser, providing guidance for device fabrication.