Metal-oxide-semiconductor capacitors fabricated by dry and wet oxidation at 1150 °C of n-type 6H–SiC exhibit a drastic negative charging during Fowler–Nordheim charge injection. This charging strongly depends on the fabrication conditions of the samples. The densities of interface states and oxide charges can be significantly reduced by a postoxidation anneal in Ar for as long as 60 min. A large part of the charge appears to be trapped at the interface. These charges are released from the traps by illumination at photon energies between 2 and 4 eV or by annealing below 300 °C. During charge injection interface states are created near the conduction band edge. Their density is strongly reduced by annealing at 150 °C. For the oxide charging we find capture cross sections in the range of 10−15–10−17 cm−2. In unannealed wet oxidized samples the traps exhibit properties similar to those of water-related traps in SiO2 on Si.

The effects of illumination on the susceptibility of ferric borate are described, and the domain structures that occur in ferric borate are discussed. It is shown that the photo-induced changes agree with a simple domain wall model, the walls probably being of the Nee1 type. The time and temperature dependence of the photo-induced increases are consistent with a localized centre model in which the centres can exist in two energy states, each with a different anisotropy. The energy reqiiired to excite the centres is received indirectly from the photons, via Fe3+ ions.

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