Energy band structure of SiO/4H-SiC interfaces and its modulation induced by intrinsic and extrinsic interface charge transfer

Watanabe, Heiji*; Kirino, Takashi*; Kagei, Yusuke*; Harries, J.; Yoshigoe, Akitaka ; Teraoka, Yuden; Mitani, Shuhei*; Nakano, Yuki*; Nakamura, Takashi*; Hosoi, Takuji*; Shimura, Takayoshi*

In this study, we investigated the energy band structure of SiO/4H-SiC fabricated on (0001) Si- and (000-1) C-face substrates by means of synchrotron radiation X-ray photoelectron spectroscopy, and discuss intrinsic and extrinsic effects of interface structure and electrical defects on the band offset modulation. It was found that valence band offset of the SiO/SiC for the C-face substrate was about 0.4 eV larger than that for the Si-face. Our photoelectron analysis revealed that the conduction band offset that determines gate leakage current and resultant gate oxide reliability of SiCMOS devices crucially depends on substrate orientation. Moreover, we found that the fixed charges accumulated at the SiO/SiC interface modulate the energy band structure to enlarge conduction band offset and that this extrinsic band structure modulation is again recovered by post treatments for defect termination.