Holmium redistribution upon solid-phase epitaxial crystallization of amorphized silicon layers

Abstract

Concentration profiles of Ho were investigated after annealing at a temperature of 620°C of silicon layers implanted with 1-MeV Ho⁺ ions to doses of 1−3×10¹⁴ cm⁻² exceeding the amorphization threshold, as well as with O⁺ ions with energies that ensure the coincidence of the concentration maxima of implanted impurities and doses that are greater by an order of magnitude than those of Ho⁺. The crystallization of the amorphized silicon layer occurs by the mechanism of solid-phase epitaxy. The main features of the segregation redistribution of Ho are shown to be similar to the previously studied segregation behavior of Er. An increase in the Ho concentration at the initial stage of the solid-phase epitaxial crystallization is explained by the small rate of mass transfer through the amorphous layer-single crystal interface. An analytical expression was obtained to describe the variation of the segregation coefficient in the process of solid-phase epitaxial crystallization, including its initial stage, which allows the calculation concentration profiles of rare-earth elements.