Impact of Surface Morphology above Threading Dislocations on Leakage Current in 4H-SiC Diodes
The impact of threading dislocation density on the leakage current of reverse IV characteristics in 1.2 kV Schottky barrier diodes (SBDs), junction barrier Schottky diodes (JBSDs), and PN junction diodes (PNDs) was investigated. The leakage current density and threading dislocation density have different positive correlations in each type of diode. For example, the correlation in SBDs is strong, but weak in PNDs. The threading dislocations were found to be in the same location as the current leakage points in the SBDs, but not in the PNDs. Nano-scale inverted cone pits were observed at the Schottky junction interface in SBDs, and it was found that leakage current increases in these diodes due to the concentration of electric fields at the peaks of the pits. These nano-scale pits were also observed directly above threading dislocations. In addition, this study succeeded in reducing the leakage current variation of 200 A-class JBSDs and SBDs by eliminating the nano-scale pits above the threading dislocations. As a result, a theoretical straight-line waveform was achieved.
Robert P. Devaty, Michael Dudley, T. Paul Chow and Philip G. Neudeck
F. Hirokazu et al., "Impact of Surface Morphology above Threading Dislocations on Leakage Current in 4H-SiC Diodes", Materials Science Forum, Vols. 717-720, pp. 911-916, 2012