Autosolitons with the charge carriers self-reproduced by impact ionization of the deep acceptor levels of indium in silicon in a strong electric field at 77 K have been experimentally detected and studied. A model describing the excitation of such impact-ionization autosolitons is proposed, in which the activating factor is the free charge carrier density and the inhibiting factor is the carrier temperature. The existence of such auto-solitons is determined by the condition that the region of high carrier density at the autosoliton center does not expand because the outdiffusion of carriers is equilibrated by their supply through thermodiffusion.