Evolution of the Substitutional Fraction on Post-Implantation Annealing in Al/4H-SiC Systems

Abstract

The problem of crystal damage recovery and of impurity substitution in implanted semiconductors is considered from a statistical mechanical viewpoint. This is done by resorting to a thermodynamic pseudo-potential originally developed for cooperative structural rearrangements in disordered systems close to their glass transition. The dependence of the substitutional fraction φ on the post-implantation annealing temperature Tann in Al/4H-SiC systems is discussed in the light of these ideas. After completion of the annealing process, an Arrhenius plot of φ(Tann) shows a slope in the order of 1 eV or less, depending on the amount of lattice damage initially produced by the implantation. Slopes ∼4 eV are found after incomplete annealing, indicating that substitution occurs mainly in damaged crystal cells. These concepts are suggested to be used for optimization of the doping procedure by ion implantation.