Abstract Numerical investigation on hole-injection characteristics of NiO/SiC heterojunction is carried out in this paper. Theory analysis and numerical simulation both indicate the excellent hole-injection characteristic of p-NiO/n-SiC heterojunction. The pn junction diode and pnp phototransistor are constructed and simulated to evaluate hole-injection characteristics p-NiO/n-SiC heterojunction. The results indicate that the p-NiO/n-SiC heterojunction shows great potential advantage in enhancing current gain of pnp phototransistor. By using NiO/SiC heterojunction as the emitter junction, the current gain of SiC based pnp phototransistor can be increased by about 96.3 times.