Redistribution of erbium during the crystallization of buried amorphous silicon layers

The redistribution of Er during its implantation in silicon at doses close to the amorphization threshold and its subsequent solid-phase epitaxial (SPE) crystallization is investigated. The formation of a buried amorphous (a) layer is discovered at Er doses equal to 5x10(13) and 1x10(14) cm(-2) using Rutherford backscattering. The segregation of Er in this case takes place inwardly from the two directions corresponding to the upper and lower boundaries of the buried alpha layer and leads to the formation of a concentration peak at the meeting place of the two crystallization fronts. A method for calculating the coordinate dependence of the segregation coefficient k from the distribution profiles of the erbium impurity before and after annealing is proposed. The k(x) curve exhibits a drop, whose width increases with decreasing Er implantation dose. Its appearance is attributed to the nonequilibrium nature of the segregation process at the beginning of SPE crystallization. (C) 1999 American Institute of Physics. [S1063-7826(99)00506-2].