Production and rearrangement of radiation defects in ion implanted semiconductors

Mechanisms of the crystalline-to-amorphous transition on ion implantation, the homogeneity of the amorphous layer, the thermal and radiation-structural rearrangements of the ion-implanted layers have been considered. The main results have been obtained by esr and reflection electron diffraction techniques. It is concluded that the amorphization mechanism proceeds in the following ways: (1) the production of the amorphous region directly in a single disordered-region (DR); (2) the interaction of the DR's with each other; and (3) the accumulation of vacancies (or interstitial atoms) at sinks in the strained region of the crystal. It is shown that the amorphous layer produced by ion implantation is heterogeneous. The essential heterogeneity has been observed in high-dose ion implantation. The necessary conditions have been formulated for the new effect of crystallization of the semi-conductor layer previously amorphized in the initial stages of bombardment. They are the following: a high, local ion-current density (30 to 100 μA/cm2), an oriented substrate, and the proper ion type and dose. (author)