Diffusion Al from implanted SiC layer

The experimental Al concentration profiles formed on implantation of Al into SiC at room temperature with subsequent high-temperature annealing are analyzed. It is shown that, at high doses above the amorphization threshold, the profiles exhibit a number of specific features: a shift of the distribution maximum, accumulation of dopant nearby the surface, and formation of box-shaped profiles. To describe quantitatively the redistribution of Al in the SiC layers implanted with high doses, the segregation-diffusion model is suggested for the first time. The model takes into account segregation of dopant between the a- and c-phases during solid-state epitaxial crystallization followed by diffusion of dopant and their evaporation from the surface. The formation of box-shaped Al profiles as a result of rapid thermal annealing is attributed to the high diffusion coefficient of dopant in the highly damaged single-crystal and polycrystalline SiC layers in the recrystallized region, and to the suppression of the enhanced transient diffusion in the remaining single-crystal part of the implanted layer.