Electrically active point defects in n-type 4H-SiC

An electrically active defect has been observed at a level position of similar to 0.70 eV below the conduction band edge (E-c) with an extrapolated capture cross section of similar to 5x10(-14) cm(2) in epitaxial layers of 4H-SiC grown by vapor phase epitaxy with a concentration of approximately 1 x 10(13) cm(-3). Secondary ion mass spectrometry revealed no evidence of the transition metals Ti, V, and Cr. Furthermore, after electron irradiation with 2 MeV electrons, the 0.70 eV level is not observed to increase in concentration although three new levels are observed at approximately 0.32, 0.62, and 0.68 eV below E-c with extrapolated capture cross sections of 4 x 10(-14), 4 x 10(-14), and 5 x 10(-15) cm(2), respectively. However, the defects causing these levels are unstable and decay after a period of time at room temperature, resulting in the formation of the 0.70 eV level. Our results suggest strongly that the 0.70 eV level originates from a defect of intrinsic nature. The unstable behavior of the electron irradiation-induced defects at room temperature has not been observed in the 6H-SiC polytype. (C) 1998 American Institute of Physics.