Abstract In this work, nanostructured nickel oxide (NSNiO) film was fabricated on 4H-SiC by using a sol–gel spin-coating process and under the optimized calcine temperature to form NSNiO/4H-SiC p-n heterojunction. The deposited film consisted of nano-sized particles with homogeneous distribution, whose diffraction peaks coincide with face-centered cubic crystalline diffraction patterns of NiO. For NSNiO film, the optical band gap was calculated as 3.75 eV, and the conductive type was analyzed to be p-type. The current density-voltage characteristic of the NSNiO/SiC p-n heterojunction showed a typical rectification behavior with a turn-on voltage of 1.16 V and a rectification ratio of about 10 3 at ± 1.5V in the dark. The results suggest that NiO/SiC structure can pave way for applying in the field of power and photoelectric devices.