Major deep levels with the same microstructures observed in n-type 4H-SiC and 6H-SiC

Abstract

Major deep levels observed in as-grown and irradiated n-type 4H–SiC and 6H–SiC epilayers have been investigated. After low-energy electron irradiation, by which only carbon atoms are displaced, five traps, EH1 (Ec−0.36 eV), Z_1/Z_2 (Ec−0.65 eV), EH3 (Ec−0.79 eV), EH5 (Ec−1.0 eV), and EH6/7 (Ec−1.48 eV), were detected in 4H–SiC and four traps, E_1/E_2 (Ec−0.45 eV), RD_5 (Ec−0.57 eV), ES (Ec−0.80 eV), and R (Ec−1.25 eV), were detected in 6H–SiC. The Z_1/Z_2, EH6/7 centers in 4H–SiC and the E_1/E_2, R centers in 6H–SiC exhibit common features as follows: their generation rates by the e^−-irradiation were almost the same each other, their concentrations were not changed by heat treatments up to 1500℃, and they showed very similar annealing behaviors at elevated temperatures. Furthermore, these defect centers were almost eliminated by thermal oxidation. Taking account of the observed results and the energy positions, the authors suggest that the Z_1/Z_2 center in 4H–SiC corresponds to the E_1/E_2 center in 6H–SiC, and the EH6/7 center in 4H–SiC to the R center in 6H–SiC, respectively. Since the concentrations of these four centers are almost the same for as-grown, electron-irradiated, annealed, and oxidized samples, these centers will contain a common intrinsic defect, most likely carbon vacancy. The authors also observed similar correspondence for other thermally unstable traps in 4H–SiC and 6H–SiC.