Ultrashallow defect states at SiO₂ 4H-SiC interfaces

Interface state density (Dit) at Si O2 4H-SiC interfaces are reported for states lying energetically within ∼0.05-0.2 eV of the conduction band edge (EC) of 4H-SiC using capacitance-voltage characterization as a function of temperature. Comparison of as-grown dry oxidized and nitrided interfaces confirms the significant reduction of Dit associated with nitridation. In the as-oxidized case (no nitridation), the Dit in the energy range ∼0.05-0.2 eV below EC is found to consist of a broad Dit peak at about ∼0.1 eV below EC with an energy width of about ∼0.2 eV and a peak magnitude of ∼2× 1013 cm-2 eV-1 superimposed on an exponentially decaying background distribution. Interfacial nitridation completely eliminates the broad peak but does not strongly affect the background.