Improvement in Electrical Properties of 4H-SiC Epilayers by Micropipe Dissociation

Abstract

In this study, the effect of micropipe dissociation via 4H-SiC vapor phase epitaxy on the electrical properties of the epilayer was investigated. Ni/4H-SiC Schottky barrier diodes (SBDs) were fabricated on a 21-µm-thick epilayer, and their reverse blocking characteristics were examined. Some micropipes dissociated into closed core screw dislocations during epitaxial growth and some of them propagated into the epilayer. The SBDs that included a propagated micropipe showed poor reverse blocking performance, as reported previously, while the breakdown voltages were below -400 V. On the other hand, the SBDs that included a dissociated micropipe withstood breakdown up to -1000 V, where the leakage current density was 10^-2 to 10^-6 A/cm². This demonstrated that a great improvement of the electrical properties could be achieved by the structural transformation of micropipes into closed core screw dislocations.