Structure of SiO2/4H-SiC interface probed by positron annihilation spectroscopy -: art. no. 014111

The structure of the SiO2/4H-SiC interface produced by dry oxidation has been studied using positron annihilation spectroscopy using energy-variable slow positron beams. Based on the Doppler broadening shape and wing parameter (S-W) correlation, the interface layer was clearly distinguished from the SiO2 and SiC layers. A single positron lifetime of 451 ps, which is sufficiently longer than that in the SiC substrate (similar to 140 ps) and close to the second lifetime in the SiO2 layer, was obtained when the incident positron energy was adjusted at the interface layer. The electron-positron momentum distribution associated with the interface layer was well explained by a theoretical calculation that considered the annihilation of the positrons by the oxygen valence electrons in the SiO2 layer. The annealing process after the oxidation resulted in the modification of the electron-positron momentum distribution in a manner similar to that of the interface traps, thereby suggesting that the interface traps correlate with the positron annihilation site.