Structure ofSiO2∕4H−SiCinterface probed by positron annihilation spectroscopy

Abstract

The structure of the ${\mathrm{SiO}}_{2}∕4\mathrm{H}\text{\ensuremath{-}}\mathrm{SiC}$ 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 ($S\text{\ensuremath{-}}W$) correlation, the interface layer was clearly distinguished from the ${\mathrm{SiO}}_{2}$ and $\mathrm{SiC}$ layers. A single positron lifetime of $451\phantom{\rule{0.3em}{0ex}}\mathrm{ps}$, which is sufficiently longer than that in the $\mathrm{SiC}$ substrate $(\ensuremath{\sim}140\phantom{\rule{0.3em}{0ex}}\mathrm{ps})$ and close to the second lifetime in the ${\mathrm{SiO}}_{2}$ 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 ${\mathrm{SiO}}_{2}$ 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.