A study of correlation between CiOi defects and dynamic avalanche phenomenon of PiN diode using He ion irradiation

Our previous research has shown that dynamic avalanche phenomenon is related to the hole trap level that is induced at an energy level of Ev+0.35 eV. In this study we will describe how we used the DLTS (deep level transient spectroscopy) method and CL (cathode luminescence) method to identify that the defects which form the hole trap level are in fact CiOi that is present in the Si wafer. We fabricated diodes using wafers with different amounts of CiOi, and conducted tests for the occurrence of the dynamic avalanche phenomenon. The results verified that the dynamic avalanche phenomenon occurs in diodes with large amounts of CiOi. By controlling the impurities in the Si wafer, we were able to improve the diode characteristics and suppress oscillation of the IGBT module current and voltage waveforms, reducing switching loss.