The migration of B in heavily-doped material was studied by using directly bonded samples. In the case of directly bonded samples of heavily doped and lightly doped Si, a pronounced tail was observed in the diffusion profile. This was attributed to the presence of mobile interstitial B plus Si interstitial complexes which originated from heavily doped material. The presence of interstitial-type defects was confirmed by stacking fault shrinkage experiments. The diffusivity of [Bi-Sii] complexes was estimated to be one or two orders of magnitude higher than the intrinsic B diffusivity. In material which was heavily doped with B, the formation of [Bi-Sii] complexes could occur via interactions between positively charged Si interstitials and ionized B during solidification. On the basis of stacking fault shrinkage experiments, the activation energies of Si interstitials were estimated to be between 2.11 and 2.5eV for P+ material, and between 3.45 and 4.11eV for float-zone material.

A Study of Boron Diffusion in Heavily-Doped Silicon. W.Wijaranakula: Journal of the Electrochemical Society, 1991, 138[4], 1131-7

Table 27

Diffusivity of B in Si/SiC Heterojunctions