Phenomenological description of ion-beam-induced epitaxial crystallization of amorphous silicon.

Abstract

In this paper we report detailed experimental measurements on the dependence of the ion-beam-induced epitaxial crystallization (IBIEC) of amorphous silicon on dopant concentration. The results show that the presence of B, P, and As dopants enhances IBIEC. In particular a logarithmic relationship between the ion-induced growth rate and dopant concentration is found for all of the impurities. In order to explain this behavior a phenomenological model of IBIEC will also be presented. The model postulates that the same defect is responsible for both thermal and ion-beam annealing. It combines the structural and electronic features of the description proposed by Williams and Elliman for conventional thermal epitaxial growth, with the intracascade approach of Jackson to the ion-assisted regrowth. Defects responsible for IBIEC are identified in kinklike steps formed onto [110] ledges at the crystalline-amorphous interface. These kinks are assumed to be generated thermally within the thermal-spike regime of each collision cascade. After defect generation, then, our approach follows Jackson's as far as the temporal evolution of defects is concerned. The model can account for all of the experimental results previously explained by the Jackson model and, moreover, can account for the doping and orientation dependences of IBIEC. This description is discussed and quantitatively compared with the experimental data.