Carbon-vacancy related defects in 4H- and 6H-SiC

Electron paramagnetic resonance (EPR) was used to study intrinsic defects in 4H- and 6H-SiC irradiated with 2.5 MeV electrons with doses ranging from 1×1017 to 2×1018 cm−2. In p-type 4H- and 6H-SiC, the dominant EPR signal, labeled EI1, associates with a defect centre having a low symmetry and an effective electron spin S=1/2. For both polytypes, its g-tensor was determined as gz=2.0015, gx=1.9962 and gy=2.0019, where gz and gx lie in the (1120) plane and the z-axis makes an angle ∼41 degrees with the c-axis. Hyperfine interaction with a 29Si atom located at two equivalent sites in the nearest neighbour shell was detected, confirming that the defect resides at the carbon site. In heavily irradiated 4H- and 6H-SiC, a new EPR spectrum having an electron spin S=1, labeled EI3, was observed. In both polytypes, the EI3 centre has a low symmetry, an isotropic g-value of 2.0063 and a fine structure parameter |D|∼5.5×10−2 cm−1. The observed hyperfine interaction with four 29Si atoms in the nearest neighbour shell confirms the involvement of the carbon vacancy in the defect. The defect is suggested to be a complex centre involving a carbon vacancy.