Reduction of deep levels generated by ion implantation into n- and p-type 4H-SiC

The authors have investigated effects of thermal oxidation on deep levels in the whole energy range of the band gap of 4H-SiC by deep level transient spectroscopy. The deep levels are generated by ion implantation. The dominant defects in n-type samples after ion implantation and high-temperature annealing at 1700 degrees C are IN3 (Z(1/2): E-C-0.63 eV) and IN9 (EH6/7:E-C-1.5 eV) in low-dose-implanted samples, and IN8 (E-C-1.2 eV) in high-dose-implanted samples. These defects can remarkably be reduced by thermal oxidation at 1150 degrees C. In p-type samples, however, IP8 (HK4: E-V+1.4 eV) survives and additional defects such as IP4 (HK0: E-V+0.72 eV) appear after thermal oxidation in low-dose-implanted samples. In high-dose-implanted p-type samples, three dominant levels, IP5 (HK2: EV+0.85 eV), IP6 (EV+ 1.0 eV), and IP7 (HK3: EV+1.3 eV), are remarkably reduced by oxidation at 1150 degrees C. The dominant defect IP4 observed in p-type 4H-SiC after thermal oxidation can be reduced by subsequent annealing in Ar at 1400 degrees C. These phenomena are explained by a model that excess interstitials are generated at the oxidizing interface, which diffuse into the bulk region. (C) 2010 American Institute of Physics. [doi:10.1063/1.3456159]