We have investigated temperature dependence (94 K–650 K) of current conduction in semi-insulating 4H-SiC epitaxial layer. The epitaxial layer was grown on highly doped n-type (0001) 4H-SiC substrate using chemical vapor deposition with dichlorosilane precursor. The current—voltage (I-V) characteristics exhibited steps at ∼1 V and ∼70 V that were attributed to the filling of deep level centers by injected electrons. Correlation of the I-V characteristics with the results of thermally stimulated current measurements showed that deep centers peaked at 242 K, 285 K, and 500 K, were responsible for the steps in the I-V characteristics. Slow processes of the injected carrier capture on traps resulted in the I-V characteristic with negative differential resistance.
We have investigated deep level centers in n-type and semi-insulating (SI) 4H-SiC epitaxial layers by thermally stimulated current (TSC) spectroscopy. The epitaxial layers were grown using chemical vapor deposition utilizing a dichlorosilane precursor. Both epitaxial layers exhibited relatively shallow levels related to Al, B, L- and D-centers. A deep level center with an activation energy of 1.1 eV, peaked at ∼400 K, was detected in the n-type epitaxial layer and correlated with the IL2 level and the 1.1 eV center in a high purity bulk SI 4H-SiC. The TSC spectra of the SI epitaxial layer was dominated by the peaks at 525–585 K that we attributed to intrinsic defects and their complexes with energy levels close to the middle of the bandgap. The TSC spectra of SI epitaxial layer exhibited peaks with different current polarity which is explained by thermoelectric effect and the built-in electric field reversal. The results of the transfer length method measurements of the SI epitaxial layer and the room temperature current-voltage (I-V) characteristics of both epitaxial layers are also reported.
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