This paper deals with an electron-paramagnetic-resonance study of the $\mathrm{Si}-B3\mathrm{}$ center, which was first reported by Daly. The $\mathrm{Si}-B3\mathrm{}$ center is a secondary defect which forms upon annealing between 50 and 175°C in irradiated boron-doped silicon and is stable up to $\approx 500$°C. Our studies indicate that the $\mathrm{Si}-B3\mathrm{}$ center exhibits only a high-temperature stress response which is indicative of a thermally activated atomic reorientation at $T\gtrsim 400$°C. This defect does not exhibit a low-temperature stress response indicative of Jahn-Teller effects; consequently, the $\mathrm{Si}-B3\mathrm{}$ center has inherent $D_{2d}$ symmetry by virtue of its molecular structure. The kinetics of this defect, the nature of the ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$ hyperfine interactions, and the symmetry of the defect suggest that the $\mathrm{Si}-B3\mathrm{}$ corresponds to either a $〈001〉$ Si di-interstitial or a $〈001〉$ Si split interstitial. The $\mathrm{Si}-B3\mathrm{}$ center appears to be similar but not identical to the $\mathrm{Si}P6\mathrm{}$ center, which Lee and Corbett have recently suggested corresponds to a $〈001〉$ Si di-interstitial.

• Received 16 September 1975

DOI:https://doi.org/10.1103/PhysRevB.14.872