Deactivation of nitrogen donors in silicon carbide

Hexagonal SiC is either co-implanted with silicon $({\mathrm{Si}}^{+})$, carbon $({\mathrm{C}}^{+})$, or neon $({\mathrm{Ne}}^{+})$ ions along with nitrogen $({\mathrm{N}}^{+})$ ions or irradiated with electrons $({\mathrm{e}}^{\ensuremath{-}})$ of $200\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$ energy. During the subsequent annealing step at temperatures above $1450\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ a deactivation of N donors and a reduction of the compensation are observed in the case of the ${\mathrm{Si}}^{+}∕{\mathrm{N}}^{+}$ co-implantation and ${\mathrm{e}}^{\ensuremath{-}}$ 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 ${({\mathrm{N}}_{\mathrm{C}})}_{4}\text{\ensuremath{-}}{V}_{\mathrm{Si}}$ 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.