We report the observation of a paramagnetic interface defect in thermally oxidized porous $n$-type doped $4H\mathrm{\text{−}}\mathrm{S}\mathrm{i}\mathrm{C}/{\mathrm{S}\mathrm{i}\mathrm{O}}_2$. Based on its axial symmetry and resolved hyperfine interactions it is attributed to an $s{p}^3$ carbon dangling bond center situated at the SiC side of the interface. This center is electrically active and pins the Fermi level in the oxidized samples. No silicon related paramagnetic dangling bond centers are observed. The formation of dangling bond centers seems to be related to interstitial oxygen diffusion at the interface during the oxidation process.

• Received 24 July 2003

DOI:https://doi.org/10.1103/PhysRevLett.92.015502