No abstract

The understanding of the structure and associated defect level of point defects in SiC is important because the material is to be used both as a semiconductor and semi-insulator. Production of the latter is achieved by compensation of unavoidable impurities using defects that require more energy for ionization than the unintentional donors or acceptors. The purpose of the present work is to measure the defect energy level of one center in high resistivity 4H SiC using photo-induced electron paramagnetic resonance (photo-EPR). The center is identified as SI-5, an EPR signal that others have attributed to the negative charge state of the carbon vacancy-carbon antisite pair, − C Si V C . Samples containing this defect exhibit two different photo thresholds, which depend on the resistivity activation energy, Ea. For samples with Ea less than 0.8 eV, a photothreshold at 0.75+/- 0.05 eV is observed, but for those with Ea greater than 0.8 eV, the threshold is between 2 and 2.5 eV. Previous work focused on the former case. Here, the SiC substrates with the larger Ea are emphasized, showing that the photo-threshold likely measures the neutral to negative defect level, − / 0 C Si V C .

Al 2 O 3 prepared by atomic layer deposition as gate dielectric on 6H-SiC(0001)Two different photothresholds of the carbon vacancy-carbon antisite pair defect ͑V C C Si − ͒ in 4H-SiC are observed using photoinduced electron paramagnetic resonance. The defect appeared after illumination with photon energy greater than 0.75 eV in two samples grown by halide chemical vapor deposition ͑HCVD͒ and one by physical vapor transport ͑PVT͒, all with activation energies ͑E a ͒ below 0.80 eV. In HCVD and PVT samples with higher activation energies, the defect was not detected with photon excitation less than 2.1 eV. The increase in V C C Si − parallels changes in the negatively charged carbon vacancy V C − in the samples with low E a . For SiC samples with high E a , the concentration of the anitisite-vacancy pair also increases with V C − and, in addition, is accompanied by a simultaneous decrease in V C + . The results are interpreted in terms of two defect levels, one for the double negative-to-negative transition of V C C Si at 0.75 eV below the conduction band edge and another for the negative-to-neutral transition of the defect at 2.1 eV above the valence band edge. The model yielding these levels also suggests that the neutral-to-negative and negative-to-double negative transitions of the isolated carbon vacancy are within a few tenths of an eV of each other and are located close to the conduction band edge.