Transient decay of persistent photoconductivity (TDPPC) measurements were performed and analyzed in terms of models in which the TDPPC is associated with thermally activated electron capture into DX and a modification of the ionized impurity density, and hence the mobility, concomitant with electron capture. Quantitative agreement between theory and experiment was possible when Chadi and Chang’s model for DX [Phys. Rev. Lett.61, 873 (1988); Phys. Rev. B39, 10063 (1989)] was employed in conjunction with a photo‐induced shallow donor.