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 extra polated capture cross section of similar to 5x10(-14) cm(2) in epitaxi al layers of 4H-SiC grown by vapor phase epitaxy with a concentration of approximately 1 x 10(13) cm(-3). Secondary ion mass spectrometry re vealed no evidence of the transition metals Ti, V, and Cr. Furthermore , after electron irradiation with 2 MeV electrons, the 0.70 eV level i s 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 e xtrapolated 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 leve ls 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 s trongly that the 0.70 eV level originates from a defect of intrinsic n ature. The unstable behavior of the electron irradiation-induced defec ts at room temperature has not been observed in the 6H-SiC polytype. ( C) 1998 American Institute of Physics.