Abstract In this work, CuAlO2 films were prepared on 4H–SiC (0001) using the sol-gel method. The surface morphology, structure and optical characteristics of the prepared films were studied. A homogeneous distribution of fine rhombohedral crystal structural grains is observed on the 4H–SiC substrate using scanning electron microscope (SEM). The film was confirmed to consist predominantly of delafossite CuAlO2 phase and impurity spinel CuAl2O4 phase via X-ray diffraction (XRD). The direct optical bandgap estimated from the measured transmittance spectra is approximately 3.85eV, while the indirect bandgap is 1.78 eV. Four emission peaks are observed in the photoluminescence (PL) spectra measured at room temperature. The emission peaks around 360 nm and 380 nm are the near band edge emission (NBE) of the prepared CuAlO2 films and the 4H–SiC substrate, respectively. The other two emission peaks around 410 nm and 470 nm arises from defects of Cu-vacancy. The fabricated p-CuAlO2/n-4H–SiC heterojunction diode exhibits typical rectification. Additionally, the turn-on voltage and rectification ratio at ± 3 V are determined to be 1.6 V and 1.26 × 103, respectively. A further 7.15 × 109 times increase of the hole injection capacity could be acquired potentially through an analysis of the energy band structure, which suggests that high injection capacity SiC bipolar devices could be feasibly achieved by utilizing CuAlO2 as the p + emitter.