Abstract: In order to solve the problem of low injection efficiency of p+n emitter junction caused by incomplete ionization of p-type SiC in bipolar SiC power devices at room temperature, our group proposed to use the heterojunction formed by wide bandgap p-type CuAlO₂ and n-type SiC as the emitter junction. In this work, CuAlO₂ thin films were prepared on 4H-SiC (0001) by sol-gel method. The influence of low heat treatment temperature range on the crystal structure, surface morphology and optical properties of CuAlO₂ thin films were studied. The results show that the formation of intermediate product CuO can be enhanced at higher heat treatment temperature, promoting the generation of CuAlO₂ phase in the solid phase reaction stage. The prepared CuAlO₂ thin films are mainly oriented with the (012) crystal orientation of CuAlO₂ phase with high crystal quality. In addition, the higher heat treatment in low temperature range is beneficial to obtain high quality CuAlO₂ thin films with uniform surface and lower concentration of Cu-vacancy defect. The surfaces of the films are uniform with an average crystal grain size of approximately 35 nm when the heat treatment temperature in low temperature range is 300 ℃. The CuAlO₂ thin films are highly transparent, with optical transmission exceeding 70% across the whole visible range. Meanwhile, the optical band gaps of the CuAlO₂ thin films increases slightly with the increase of heat treatment temperatures in low temperature range.

Key words: SiC, sol-gel method, CuAlO₂ thin film, heat treatment at low temperature, optical band gap