MOSSBAUER SEARCH FOR CO-ACCEPTOR PAIRS IN SI

Mossbauer spectroscopy was used to study the formation and stability o f Co-acceptor complexes after diffusion of Co-57 in heavily B-, Al-, G a- and In-doped silicon. The Fe-57 MS-spectra recorded after diffusion and quench show a dominating line complex (with an absorber isomer sh ift between +0.7 and +1.0 mm/s relative to alpha-Fe), previously attri buted to Co-acceptor pairs. Upon annealing a transformation of this Co -complex is observed, and activation energies are derived in the range of 1.4 to 1.8 eV, much larger than expected for the dissociation of C o-acceptor pairs. Possible reasons for this discrepancy are discussed.