E(1)/E(2) (E(C)-0.36/0.44eV) 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 V(Si)-complex. With positron lifetime technique, we have identified V(Si) and V(C)V(Si) in the Lely grown n-type 6H-SiC sample, with V(Si) annealed out at 650degreesC. Concentration of V(C)V(Si) persists at 1400degreesC annealing and significantly decreased after the 1600degreesC annealing. Considering the deep level transient spectroscopic (DLTS) results on the neutron irradiated n-type SiC epi sample that E(1)/E(2) completely disappeared after the 1400degreesC annealing, E(1)/E(2) is not the V(C)V(Si) defect. With positron annihilation techniques, Rempel et al [1] have shown the energy dependence of vacancy generated by electron irradiation. With low irradiation energy of 0.3MeV, only V(C) was generated and at higher energy (0.5 MeV), Si vacancy was detected. With focus to find the minimum energy for generating E(1)/E(2), we have performed DLTS studies on n-type epi 6H-SiC materials irradiated by electrons with varying energies. Our results suggest that E(1)/E(2) have microstructure related to a carbon vacancy or a carbon interstitial.