Relationship between defects induced by irradiation and reduction of hole concentration in Al-doped 4H–SiC

Abstract

From the temperature dependence of the hole concentration in lightly Al-doped 4H–SiC epilayers, a shallow acceptor with E V + 0.2 eV , which is an Al atom ( Al Si ) at a Si sublattice site, and an unknown deep defect with E V + 0.35 eV are found, where E V is the valence band maximum. In unirradiated epilayers, moreover, the density ( N Defect ) of this defect is close to the Al acceptor density ( N Al ) . With irradiation of 0.2 MeV electrons, the N Al is reduced, while the N Defect is increased. Judging from the minimum electron energy required to displace a substitutional C atom ( C s ) or Al Si , the bond between Al Si and its nearest neighbor C s is broken due to the displacement of the C s by this irradiation. Moreover, the displacement of the C s results in the creation of a complex ( Al Si – V C ) of Al Si and its nearest neighbor C vacancy ( V C ) , indicating that the possible origin of the defect with E V + 0.35 eV is Al Si – V C .