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

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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 (Ec). The most prominent and stable ones occur at Ec−0.70eV (labeled Z1∕2) and Ec−1.60eV(EH6∕7). After exhibiting a multistage annealing process over a wide temperature range, presumably caused by reactions with migrating defects, a significant fraction of both Z1∕2 and EH6∕7 (25%) still persists at 2000 °C and activation energies for dissociation in excess of 8 and ∼7.5eV are estimated for Z1∕2 and EH6∕7, respectively. On the basis of these results, the identity of Z1∕2 and EH6∕7 is discussed and related to previous assignments in the literature.