Isochronal Annealing of Silicon‐Phosphorus Solid Solutions

Isochronal annealings of 500 hr per pulse, in steps of 25°C, have been performed in the range 400°–800°C on silicon single crystals of well‐known composition bulk‐doped with phosphorus. Dopant concentrations were . The annealing curves, determined by electrical resistivity measurements, are reported and discussed. A resistivity increase, attributed to phosphide precipitation, takes place above 400°C in the dopant richest alloy. It is noticed that a high density of dislocations (about 10⁸ cm⁻²) does not alter the kinetics of this process. At 550°C coherent precipitates of interstitial character have been observed by TEM; their density and mean size are consistent with a composition. The features of the defects associated with the dissolution process are also reported. Phosphorus diffusivity for precipitation, calculated at 550°C, turns out to be about five orders of magnitude higher than expected from extrapolation of well‐known high temperature values. The solubility of phosphorus in silicon, determined by the kinetics of recovery of resistivity, results as about at 650°C.