A review was presented of various shallow and deep acceptor centres in 9Be-doped samples of 6H-type material. Electron paramagnetic resonance (95GHz) and electron-nuclear double resonance measurements were used to determine their g, hyperfine and quadrupole tensors. Up to 8 different centres were identified. The geometrical and electronic structures of these centres resembled those of B-related centres in 6H-type material. Three of them exhibited the behavior that was characteristic of shallow B centres, and 5 of them exhibited the behavior that was characteristic of deep centres. Three of the deep centres, which had their symmetry axis along the c-axis, were similar to the centres which were found in B-doped 6H-type material. The 2 other centres had their symmetry axis at 70º to the c-axis, and these had not been found in B-doped 6H-type material. This appeared to be the first time that deep Be acceptor centres had been reported. The shallow centres consisted of a negatively charged Be ion which substituted for a Si atom, BeSi, with the main spin density (30%) being located in a dangling pz orbital on the nearest-neighbour C atom. The deep centres consisted of a BeSi-C-vacancy pair; with the main spin density (75 to 90%) being located on the three Si atoms on the other side of the vacancy. In as-grown Be-doped samples, the electron paramagnetic resonance lines of the deep centres were either absent or were much weaker than those in the Be diffusion sample. This was explained by assuming that the diffusion of Be introduced more vacancies than in as-grown samples; thus leading to a high concentration of deep centres.

Electronic Structure of the Be Acceptor Centers in 6H-SiC. A.Van Duijn-Arnold, J.Schmidt, O.G.Poluektov, P.G.Baranov, E.N.Mokhov: Physical Review B, 1999, 60[23], 15799-809