EXTENDED X-RAY-ABSORPTION FINE-STRUCTURE STUDY OF THE LOCAL ATOMIC-STRUCTURE IN AS+ HEAVILY IMPLANTED SILICON

Extended x-ray-absorption fine-structure (EXAFS) measurements were performed on As heavily implanted crystalline silicon, using total electron yield and fluorescence detection to study a large range of implanted doses: 5 X 10(15), 3, and 5 X 10(16) As/cm2. The electrical deactivation of these samples after laser and subsequent thermal annealing (from 350-degrees-C up to 1000-degrees-C) is studied through the evolution of the first two shells of neighbors around As atoms. For an annealing temperature lower than 750-degrees-C, a model consistent with the EXAFS results is presented, in which the As deactivation is due to the formation of inactive clusters involving about 7 As atoms around one vacancy. For a higher annealing temperature (750-1000-degrees-C) the EXAFS results suggest the coexistence of clusters and precipitates in equilibrium.