Interface state density (Dit) at SiO2∕4H–SiC interfaces are reported for states lying energetically within ∼0.05–0.2eV 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 ∼0.05–0.2eV below EC is found to consist of a broad Dit peak at about ∼0.1eV below EC with an energy width of about ∼0.2eV and a peak magnitude of ∼2×1013cm−2eV−1 superimposed on an exponentially decaying background distribution. Interfacial nitridation completely eliminates the broad peak but does not strongly affect the background.

Postoxidation annealing in nitric oxide ͑NO͒ results in a significant reduction of electronic states at SiO 2 / 4H-SiC interfaces. Measurements of electron trapping dynamics at interface states in both thermally oxidized and NO annealed SiO 2 / 4H-SiC interfaces were performed using constant-capacitance deep level transient spectroscopy ͑CCDLTS͒ and double-CCDLTS. We show that the interface state density in as-oxidized samples consists of overlapping distributions of electron traps that have distinctly different capture cross sections. The dominant trap distributions, centered at E c − 0.24 eV with ϳ 7 ϫ 10 −19 cm 2 , and at E c − 0.46 eV with ϳ 4 ϫ 10 −17 cm 2 are passivated by NO annealing. The remaining interface states all have capture cross sections in the range 10 −19 −10 −21 cm 2 .

No abstract