Fabrication of silicon and carbon based wide-gap semiconductor thin films for high conversion efficiency

Nitrogen doped amorphous silicon carbide (N-doped a-SiC) thin films were fabricated by radio frequency plasma enhanced chemical vapor deposition (RF-PeCVD) method using mixed solution of tetramethylsilane (TES) and 1,1,1,3,3,3-hexamethyldisilazane (HMDS) as a liquid source. Chemical composition of N-doped a-SiC thin film was Si:C 1:4 and sp²-bonded carbon ratio was 0.75. N-doped DLC were multi-phase structure including a-SiC phase, sp ² clusters and a-Si clusters. Optical gap and resistivity of the film were 1.68 eV and 4.32×10⁴ Ω cm, respectively. From photocurrent measurement under UV exposure, it was clarified that the film functioned as n-type semiconductor materials with 4.87 % of quantum yield, which was on the same level as that obtained at anatase-type titanium oxide prepared by sol-gel method. To apply these films to solar cells, further improvements of optical gap and conductivity are necessary.