In this paper, a through dose parameter Фa/c, which is defined by the dose of ions passing through the amorphous/ crystal (a/c) interface, is proposed, and the use of Фa/c combined with parameters for ion-implantation profiles to model the thickness of the amorphous layer da is demonstrated. It is shown that Фa/c is independent of ion-implantation conditions but depends on the impurities.Фa/c for Ge, Si, As, P, B, In, and Sb is evaluated. Consequently, da over a wide range of ion-implantation conditions for various ions was predicted.