Abstract Electron irradiation was performed to enhance the switching speed and thereby to reduce the energy loss of a p–n junction diode. The reverse recovery time decreased significantly but other electrical deterioration such as leakage current and on-stage voltage drop due to the electron irradiation was found not to be much. Also the defect distribution and the type of the electron irradiation-induced defects are discussed based on the deep level transient spectroscopy (DLTS) analysis results and the secondary ion mass spectrometry (SIMS) depth profiles of the silicon substrate.