Electronic and atomic structure of the boron-vacancy complex in silicon

In electron-irradiated boron-doped silicon the electron paramagnetic resonance spectrum Si-G10 has been studied. Earlier this spectrum had tentatively been identified with a boron-vacancy complex in a next-nearest-neighbor configuration. With electron-nuclear double resonance the hyperfine and quadrupole interactions with ¹⁰B (nuclear spin I=3) and ¹¹B (I=(3/2)) could be determined, and thus the presence of boron be proved. These experimental results turned out to be consistent with the original microscopic model proposed by Watkins. Because of the low triclinic symmetry of the defect, no symmetry-related neighbor sites exist. As a result every neighbor position with a ²⁹Si nucleus gives rise to a distinct hyperfine tensor. Therefore, hyperfine interactions with only eight neighboring ²⁹Si nuclei have been determined. These hyperfine data showed that the distant boron atom causes only a small deviation from mirror-plane symmetry. This observation made it possible to assign six of the hyperfine interaction tensors to specific lattice sites. From the observed hyperfine interactions it was deduced that this neutral BV⁰ complex is rather a B⁺{V}^{{{-}}}$ structure. This model is further supported by the interpretation of the boron quadrupole interaction.