Diffusion of gold into heavily boron-doped silicon

Diffusion of Au into dislocation-free and highly dislocated Si with high B-background doping levels has been investigated with the aid of neutron activation analysis in conjunction with mechanical sectioning. The high B-doping level causes extrinsic conditions, i.e., the hole concentration exceeds the intrinsic carrier concentration even at diffusion temperatures between 900 degrees C and 1100 degrees C. All profiles are accurately described on the basis of the kick-out diffusion model and a mechanism which takes into account segregation of Au at dislocations. Our analysis provides solubility data C-Au(eq) of Au in Si and effective diffusion coefficients D-Aui,I(eff) related to interstitial Au and Si self-interstitials I The dependence of these quantities on the B-background doping level is well described by the Fermi-level effect. This analysis supports singly positively charged states in p-type Si of Au on interstitial (Au-i) and substitutional (Au-s) sites and of Si self-interstitials Successful fitting of C-Au(eq) additionally requires an acceptor level of Au-s. The electrical properties deduced for Au-i, Au-s, and I are summarized in Table 2. Au profiles in highly dislocated Si obtained especially after diffusion at 900 degrees C give evidence of Au trapped at dislocations. From our preliminary experimental results we determine an enthalpy difference of 2.7 eV between Au on substitutional sites and Au captured at dislocations.