In this work, electrical breakdown and the origin of reverse leakage current in 4H-SiC/Ni Schottky barrier diodes without edge termination and passivation were Studied. Experimental results indicate that the SiC surface surrounding the metal contact and triple-junction region, rather than crystallographic defects in the epitaxial layer, were responsible for high leakage current and premature breakdown of the as-fabricated diodes. A post-fabrication Surface treatment was implemented to investigate the surface contribution to leakage current and breakdown voltage. The diodes exposed to surface treatment exhibit breakdown voltage of about 1000 V or more, which is about two times higher than that of as-fabricated diodes and about 25% of the breakdown voltage for the parallel plane abrupt junction based on the epi-layer blocking capability. Experimental data describing the breakdown-related behavior of the SBDs along with surface-controlled leakage current and breakdown are given, which can be useful for researchers developing SBDs. Issues related to practical applications are also addressed. (C) 2008 Elsevier Ltd. All Fights reserved.