An overview of various shallow and deep acceptor centres in 9Be-doped 6H-type material was presented. Electron paramagnetic resonance (95GHz) and electron-nuclear double resonance methods were used to determine the properties of up to 8 different centres. The geometrical and electronic structures of these centres resembled those of B-related centres in this material. Three of them exhibited a behavior which was characteristic of shallow B centres, and 5 of them exhibited a behavior which was characteristic of deep centres. Three of the deep centres, with their symmetry axis along the c-axis, were similar to the centres which were found in B-doped material. The other two had symmetry axes which were at 70º to the c-axis. This appeared to be the first time that deep Be acceptor centres had been reported. The shallow centres consisted of a negatively charged Be which replaced a Si atom, BeSi; with the main spin density (30%) being located in a dangling 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 absent; or were much weaker than those in the Be diffused sample. This was explained by assuming that Be diffusion introduced more vacancies; 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