Deactivation of nitrogen donors in silicon carbide

Hexagonal SiC is either co-implanted with silicon (Si⁺), carbon (C⁺), or neon (Ne⁺) ions along with nitrogen (N⁺) ions or irradiated with electrons (e^-) of 2000.3em0exkeV energy. During the subsequent annealing step at temperatures above 14500.2em0ex^∘C a deactivation of N donors and a reduction of the compensation are observed in the case of the Si⁺∕N⁺ co-implantation and e^- irradiation. The N donor deactivation is investigated as a function of the concentration of the co-implanted species and the annealing temperature. The formation of energetically deep defects is analyzed with deep level transient spectroscopy. A detailed theoretical analysis based on the density functional theory is conducted; it takes into account the kinetic mechanisms for the formation of N interstitial clusters and (N-vacancy) complexes. In accordance with all the experimental results, this analysis distinctly indicates that the (NC)₄-VSi complex, which is thermally stable at high temperatures and which has no level in the band gap of 4H-SiC, is responsible for the N donor deactivation.