Annealing behavior between room temperature and 2000 °C of deep level defects in electron-irradiated n-type 4H silicon carbide

The annealing behavior of irradiation-induced defects in 4H-SiC epitaxial layers grown by chemical-vapor deposition has been systematically studied by means of deep level transient spectroscopy (DLTS). The nitrogen-doped epitaxial layers have been irradiated with 15-MeV electrons at room temperature and an isochronal annealing series from 100 to 2000 °C has been performed. The DLTS measurements, which have been carried out in the temperature range from 120 to 630 K after each annealing step, revealed the presence of six electron traps located in the energy range of 0.45–1.6 eV below the conduction-band edge $\left(E_c\right)$ . The most prominent and stable ones occur at $E_c-0.70\mathrm{eV}$ (labeled $Z_{1∕2}$ ) and $E_c-1.60\mathrm{eV}\left(E{H}_{6∕7}\right)$ . After exhibiting a multistage annealing process over a wide temperature range, presumably caused by reactions with migrating defects, a significant fraction of both $Z_{1∕2}$ and $E{H}_{6∕7}$ (25%) still persists at 2000 °C and activation energies for dissociation in excess of 8 and $\sim 7.5\mathrm{eV}$ are estimated for $Z_{1∕2}$ and $E{H}_{6∕7}$ , respectively. On the basis of these results, the identity of $Z_{1∕2}$ and $E{H}_{6∕7}$ is discussed and related to previous assignments in the literature.