The photoelectromagnetic effect (PEM effect) on indium‐implanted silicon was examined as a function of ion dose in the range 1014–1015ions/cm2and as a function of annealing up to 800°C. The experimental results indicated that the measurements of the PEM voltage can be utilized as a means of detecting changes in lattice ordering in ion‐implanted silicon that were caused by the annealing treatment. Combining the results of the PEM voltage measurements with those of electron diffraction examinations, it was found that crystal reordering in In‐implanted silicon by postannealing occurred from an inward part of the host crystal rather than from the ion‐implanted surface.