Prominent defects in semi-insulating SiC substrates

Progresses in defects characterization of high-purity semi-insulating (HPSI) SiC substrates are reviewed. The vacancies, divacancy, and carbon vacancy–carbon antisite pairs were found to be dominating defects in HPSI 4H-SiC substrates with the thermal activation energy Ea in the range ∼0.6–1.6 eV. Several vacancy-related deep acceptor levels were estimated and suggested to be responsible for the semi-insulating (SI) behavior in substrates with different Ea. Deep levels associated with different activation energies are suggested. Annealing behavior of vacancy-related defects and the stability of the SI properties were studied. Prominent defects in SI 4H-SiC substrates doped with vanadium (V) were identified. Activation energies of Ea∼1–1.1 eV were observed for V-doped samples with the V concentration ranging from 5.5×1015 to 1.1×1017 cm−3. Our results show that only in heavily V-doped samples, the activation energy Ea∼1 eV is related to V, whereas in moderate V-doped materials, the SI properties are determined by intrinsic defects.