The Correlation of Surface Defects and Reverse Breakdown of 4H-SiC Schottky Barrier Diodes

Surface defect characterization and the influence of selected surface defects on the reverse characteristics of 4H-SiC Schottky barrier diodes (SBDs) are investigated, with particular emphasis on comet and carrot defects. Premature breakdown caused by comets occurs at voltages below 250 V for an SBD with ideal parallel plane breakdown of 1,600 V. The location of comets relative to the Schottky contact ultimately determines the reverse characteristics of the device. The reverse breakdown voltage of SBDs with carrot defects can be more than 1,000 V, but the reverse leakage current is about two orders higher than that of a defect-free SBD. The SBDs of diodes with and without carrots are 1.01 eV and 1.44 eV, respectively. The SBDs, which catastrophically fail during reverse bias measurement, are investigated as well. The average breakdown voltage of SBDs, which failed catastrophically, is about 745 V. According to the experimental observations, catastrophic failures are not associated with obvious surface defects, crystallographic directions, or postimplant annealing time.