The defects formed in a 6H-SiC p+n diode by irradiation with 1 MeV electrons have been studied by both single-alpha-particle-induced charge transient spectroscopy and conventional deep level transient spectroscopy (DLTS). The charge collection efficiency was significantly degraded by the electron irradiation. A radiation-induced defect (X) was observed by charge transient spectroscopy. We assign this defect to the electron trap Ei already known in literature and observed by us with DLTS, as its activation energy, 0.50 eV, and annealing behavior, are similar. Moreover, as peaks related to X/Ei disappear after annealing at 250°C and charge collection efficiency also significantly recover after annealing at 250°C, we conclude that this defect is mainly responsible for the decreased charge collection efficiency.