Intrinsic defects in semi-insulating SiC: Deep levels and their roles in carrier compensation

Vacancies, divacancies and carbon vacancy-carbon antisite pairs are found by electron paramagnetic resonance (EPR) to be dominant defects in high-purity semi-insulating (HPSI) 4HSiC substrates having different thermal activation energies of the resistivity ranging from -0.8 eV to similar to 1.6 eV. Based on EPR results and previously reported data, the energy positions of several acceptor states of the vacancies and vacancy-related complexes are estimated. These deep levels are suggested to be associated to different thermal activation energies and responsible for the semi-insulting behaviour in HPSI SiC substrates. Their role in carrier compensation is discussed.