Tadashi Misumi

Analysis of Dynamic Avalanche Phenomenon of PiN Diode Using He Ion Irradiation

The purpose of this paper is to analyze the dynamic avalanche phenomenon of conventional PiN diodes using He ion irradiation. In conventional PiN diodes, the avalanche occurs during reverse recovery operation under high voltage and low temperature conditions, resulting in two peaks and high frequency oscillation in the recovery current. The two peaks in the current were reproduced by a simulation that introduces hole trap levels. It was also confirmed that the phenomenon can be suppressed by lowering the density of the trap levels or the minority carrier lifetime of the bulk wafer

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.

Effects of Trap Levels on Reverse Recovery Surge of Silicon Power Diode

In this paper, we report on the effects of trap energy levels on the reverse recovery surge, for the first time. The different current and temperature dependences of the reverse recovery surge with shallow and deep trap energy levels were measured. Results of simulations of current and temperature dependences of the reverse recovery surge with different trap energy levels were similar to measurement results. Through numerical and theoretical analyses based on the Shockley–Read–Hall (SRH) model, it was confirmed that variations in recombination rate due to different trap energy levels affect the current and temperature dependences of the reverse recovery surge. We found that in order to achieve a soft recovery in the design of silicon power diodes, the trap energy levels play a crucial role along with the carrier lifetime profile.