The role of solitons and the kinetics of precipitate growth in boron doped silicon–germanium alloys

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Abstract
The time dependence of the thermoelectric transport properties of boron doped Si70Ge30 alloys has been investigated for times between 1 and 8700 h at an isothermal heat treatment temperature of 1100 K. Changes in the Seebeck coefficient, electrical resistivity, and carrier concentration which result from the precipitation of boron are reported. Three distinct stages are observed in the precipitation process: (a) an initial stage of precipitate zone growth lasting for about 1000 h characterized by a parabolic rate law, (b) a final stage commencing after about 4000 h and obeying the conventional Lifshitz–Slyozov post nucleation rate law, and (c) a lengthy intermediate stage lasting for about 3000 h in which the transition from initial to final stage takes place. A recently proposed soliton model for the kinetics of precipitate growth in binary phase systems is found to correctly reproduce the experimental observations. It is also reported that the precipitation process is reversible and the precipitated boron can be put back into solid solution by high temperature annealing.