Defect energy levels in electron-irradiated and deuterium-implanted6Hsilicon carbide

Using deep-level transient spectroscopy, we studied defect energy levels and their annealing behavior in nitrogen-doped $6H-\mathrm{SiC}$ epitaxial layers irradiated with 2-MeV electrons and implanted with 300-KeV deuterium or hydrogen at room temperature. Five levels located at $E_c-0.34,$ $E_c-0.41,$ $E_c-0.51,$ $E_c-0.62,$ and $E_c-0.64\mathrm{}\mathrm{eV}$ consistently appear in various samples grown by chemical vapor deposition, showing they are characteristic defects in n-type $6H-\mathrm{SiC}$ epitaxial layers. It is suggested that the $E_c-0.51\mathrm{}\mathrm{eV}$ level originates from a carbon vacancy, and that the two levels at $E_c-0.34\mathrm{}$ and $E_c-0.41\mathrm{}\mathrm{eV},$ which likely arise from the occupation of inequivalent lattice sites, and the level at $E_c-0.51\mathrm{}\mathrm{eV}$ are different charge states of the carbon vacancy. The annealing kinetics of the $E_c-0.51\mathrm{}\mathrm{eV}$ level are first order with an activation energy of 1.45 eV, and a level at $E_c-0.87\mathrm{}\mathrm{eV}$ growing upon its decay arises most likely from a vacancy-impurity complex. The results for the $E_c-0.62\mathrm{}\mathrm{eV}$ and $E_c-0.64\mathrm{}\mathrm{eV}$ levels are consistent with a defect model involving a silicon vacancy on inequivalent sites in the $6H$ lattice. Furthermore, the present results show that at hydrogen doses of ${10}^{11}{\mathrm{cm}}^{\mathrm{-}2}$ no interaction between hydrogen and the irradiation-induced silicon vacancy takes place even after annealing at temperatures up to 800 °C, in contrast to the results reported for n-type silicon.