We used a 193-nm ArF excimer laser to produce a surface functional layer with a tunable Schottky barrier height (SBH) on the n-type 4H-SiC surface. The SBHs of the laser-modified layer/SiC contact ranged from 0.38 +/- 0.05 to 1.82 +/- 0.1 eV. We evaluated the I-V characteristics of Schottky barrier diodes (SBDs) and investigated their corresponding nanoscale current transport characteristics across the laser-modified layer/4H-SiC interface. We attributed changes of the interfacial transport properties between Au and SiC to the laser-induced formation of SiOx/Si compounds with oxygen vacancies in the nitrogen-doped (N-doped) defective graphitic structure. Density functional theory calculations suggested that defect oxide in the SiOx/Si decreased the Schottky barrier width and increased the direct electron tunneling current. Furthermore, the Fermi level of the laser-induced N-doped defective graphitic structure shifted towards the conduction band compared with that of pristine graphene, which was also beneficial for reducing the SBH. This study provides a novel understanding of the interfacial interactions of a laser-modified layer on SiC through nanoscale electrical analysis. These findings will be useful for further investigations of SiC-based nano-photoelectric devices.