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

摘要

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℃ 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 (E_c). The most prominent and stable ones occur at E_c-0.70 eV (labeled Z_(1/2)) and E_c-1.60 eV(EH_(6/7)). 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 EH_(6/7) (25%) still persists at 2000℃ and activation energies for dissociation in excess of 8 and ?7.5 eV are estimated for Z_(1/2) and EH_(6/7), respectively. On the basis of these results, the identity of Z_(1/2) and EH_(6/7) is discussed and related to previous assignments in the literature.