Isothermal annealing study of the EH1 and EH3 levels in n-type 4H-SiC

Particle irradiation is known to give rise to several majority carrier traps in the band gap of n-type 4H-SiC, in the 0.4-1.6 eV energy range below the conduction band edge (E_C). Among these traps, the EH1 (E_C-0.4 eV) and the EH3 (E_C-0.7 eV) are the least thermally stable ones and not much is known on their microscopic origin. In order to understand the nature of EH1 and EH3, their annealing kinetics was studied by means of deep level transient spectroscopy and the results were interpreted by invoking the diffusion-limited theory. It is found that EH1 and EH3 are two different charge states of the same defect, labeled EH-center, that anneals out with an activation energy of ∼1.1 eV and whose nature is related to a carbon interstitial. Our study shows that the EH-center is not the same as the S-center defect which was reported by previous studies found in the literature.