Morphological defects and elementary screw dislocations in 4H–SiC were studied by high voltage Ni Schottky diodes. Micropipes were found to severely limit the performance of 4H–SiC power devices, whereas carrot-like defects did not influence the value of breakdown voltage. The screw dislocation density as determined by x-ray topography analysis under the active area of the diode was also found to directly affect the breakdown voltage. Only diodes with low density of screw dislocations and free from micropipes could block 2 kV or higher.

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