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Interface trap passivation at the SiO2∕carbon-terminated (0001¯) face of 4H-SiC utilizing nitridation and hydrogenation has been evaluated. The SiO2∕SiC interface, created by dry thermal oxidation on the C face, shows appreciably higher interface state density near the conduction band compared to the (0001) Si face. A postoxidation anneal in nitric oxide followed by a postmetallization anneal in hydrogen results in dramatic reduction of the trap density by over an order of magnitude near the conduction band. The electrical measurements have been correlated with the interfacial chemistry.

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Nitric oxide postoxidation anneal results in a significant decrease of defect state density (Dit) near the conduction bandedge of n-4H–SiC at the oxide/(112̄0) 4H–SiC interface. Comparison with measurements on the conventional (0001) Si-terminated face shows a similar interface state density following passivation. Medium energy ion scattering provides a quantitative measure of nitrogen incorporation at the SiO2/SiC interface.

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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 .

Generation lifetimes and interface state densities of n-type 4H-SiC metal oxide semiconductor (MOS) capacitors are characterized by using the pulsed MOS capacitor technique. A decrease in lifetime and increase in interface state density occurs when the devices are negatively biased at 400°C. This behavior is consistent with an effect seen in Si∕SiO2 devices known as negative bias temperature instability. A portion of the lifetime degradation caused by this effect can be recovered by removing the negative bias as well as by positively biasing the device.