The reactivation kinetics of passivated boron acceptors in hydrogenated silicon during zero bias annealing in the temperature range of 65–130 °C are reported. For large annealing times and high annealing temperatures, the reactivation process follows second-order kinetics and is rate limited by a thermally activatedH˜2complex formation process. For short annealing times and low annealing temperatures, the reactivation rate is found to be larger than that due toH˜2complex formation alone. We conclude that the faster reactivation is caused by the diffusion of the liberated hydrogen atoms into the bulk as well asH˜2complex formation. The effective diffusion coefficient of hydrogen is measured and found to obey the Arrhenius relation with an activation energy (1.41±0.1) eV. ©1997 American Institute of Physics.