Nickel distribution in crystalline and amorphous silicon during solid phase epitaxy of amorphous silicon

Solid phase epitaxy of nickel-doped amorphous silicon (a-Si) films on cryst alline silicon (c-Si) substrates has been investigated. The crystallization mode of the a-Si films depends strongly on the nickel concentration. Below similar to 5 x 10(18) Ni/cm(3), redistribution of nickel into the c-Si sub strate occurs and the regrowth process is controlled by an "ordinary'' ther mally activated solid phase epitaxial crystallization (SPEC) process. In co ntrast, above 5 x 10(18) Ni/cm(3) segregation of Ni in the a-Si films is ob served and the silicon crystallization is driven by impurity enhanced SPEC and/or silicide mediated crystallization in the bulk of the amorphous film. The redistribution of Ni during crystallization can be described in terms of an effective distribution coefficient accounting for the actual crystall ization rate of a-Si and the Ni diffusivity in a-Si. Further, dissolution o f implantation-induced (311) defects is observed in the samples exhibiting Ni diffusion into the crystalline phase during ordinary SPEC. This indicate s annealing and/or suppression of the (311) defects due to nickel accumulat ing in the region of end-of-range defects. (C) 1998 American Institute of P hysics. [S0021-8979(98)06124-6].