AGGREGATION EQUILIBRIA IN ARSENIC DOPED SILICON

Carrier density profile determinations are reported which confirm that a mass action relation holds between the ionized and the inactive mob ile As in silicon. Experiments were performed under equilibrium condit ions at temperatures in the range 780-885-degrees-C. The carrier densi ty n versus the dopant concentration N(T) exhibits a very pronounced s aturation behaviour which is compared with the one expected in well kn own cluster models. These results complement the recent finding that t he inactive As can exist in equilibrium with the monoclinic SiAs. From this information and previous SAXS, TEM, and EXAFS results one can co nclude that a pre-precipitation phenomenon, with its inherent cluster distribution, is responsible for the inactive As.