Defect energy levels in hydrogen-implanted and electron-irradiated n-type 4H silicon carbide

Abstract

Using deep level transient spectroscopy (DLTS), we have studied the energy position and thermal stability of deep levels in nitrogen doped 4H–SiC epitaxial layers after 1.2MeV proton implantation and 15MeV electron irradiation. Isochronal annealing was performed at temperatures from 100to1200°C in steps of 50°C. The DLTS measurements, which were carried out in the temperature range from 120to630K after each annealing step, reveal the presence of ten electron traps located in the energy range of 0.45–1.6eV below the conduction band edge (Ec). Of these ten levels, three traps at 0.69, 0.73, and 1.03eV below Ec, respectively, are observed only after proton implantation. Dose dependence and depth profiling studies of these levels have been performed. Comparing the experimental data with computer simulations of the implantation and defects profiles, it is suggested that these three new levels, not previously reported in the literature, are hydrogen related. In particular, the Ec−0.73eV level displays a very narrow depth distribution, confined within the implantation profile, and it originates most likely from a defect involving only one H atom.