Valence band offset and hole injection at the 4H-, 6H-SiC/SiO2 interfaces

The valence band offset between 4H-, 6H-SiC, and grown-on thermal oxide is directly measured using internal photoemission of holes. The obtained value ΔEV=2.9±0.1 eV in combination with the earlier reported barrier for valence electrons yields an oxide band gap width of 8.9 eV, close to the intrinsic value for amorphous SiO2 which suggests an abrupt SiC/SiO2 interface. Hole tunneling from SiC into SiO2 is mediated by oxide defect states distributed in an energy range of ∼1 eV above the SiO2 valence band.