Identities of the deep level defects E1/E2 in 6H silicon carbide

E1/E2 (EC-0.36/0.44 eV) are deep level donors generally found in ion-implanted, electron and neutron irradiated n-type 6H-SiC materials. Their configurations are controversial and have been related to a negatively charged carbon vacancy, a divacancy or a VSi-complex. With positron lifetime technique, we have identified VSi and VCVSi in the Lely grown n-type 6H-SiC sample, with VSi annealed out at 650 C. Concentration of VCVSi persists at 1400 C annealing and significantly decreased after the 1600 C annealing. Considering the deep level transient spectroscopic (DLTS) results on the neutron irradiated n-type SiC epi sample that E1/E2 completely disappeared after the 1400 C annealing, E1/E2 is not the VCVSi defect. With positron annihilation techniques, A. A. Rempel et al (2002) have shown the energy dependence of vacancy generated by electron irradiation. With low irradiation energy of 0.3MeV, only VC was generated and at higher energy (0.5MeV), Si vacancy was detected. With focus to find the minimum energy for generating E1/E2, we have performed DLTS studies on n-type epi 6H-SiC materials irradiated by electrons with varying energies. Our results suggest that E1/E2 have microstructure related to a carbon vacancy or a carbon interstitial. (orig.)