Radiotracer identification of a Ta-related deep level in 4H-SiC

To identify tantalum-related deep levels, deep level transient spectroscopy (DLTS) measurements were performed on Ta-implanted n-type 4H-silicon carbi de. The DLTS spectra of samples implanted with stable Ta-181 exhibit one do minating peak representing a trap energy of about E-T=E-C-0.67 eV. Due to s uperimposed signals of intrinsic defects, the exact value depends on the an nealing conditions. To achieve a definite assignment of this peak to tantal um, the radioactive isotope Ta-177 was recoil implanted into n-type 4H-SiC. DLTS spectra measured subsequently during the nuclear decay of Ta-177 to H f-177 reveal a trap with decreasing concentration according to the elementa l transmutation. This effect definitely proofs the identification of a Ta-r elated level at 0.68 eV below the conduction band edge. There is no further DLTS peak of time-dependent height, indicating that there is no deep level of Hf in the part of the band gap investigated. (C) 2000 American Institut e of Physics. [S0021-8979(00)06519-1].