Reverse Leakage Current Instability of Power Fast Switching Diodes Operating at High Junction Temperature

Some power electronics applications reveal performance weakness of fast recovery silicon diodes, in spite of significant advance made in their switching performance. The maximum operation junction temperature, specified in the data sheets is usually limited to 150 degC. Typical I-V reverse characteristics from room to high temperature, taken from commercial fast recovery diodes, available at this time are presented. Instability of the electrical characteristic is exhibited above 125 degC. A comparison between fast recovery and similar standard recovery diodes is made. For high voltage fast recovery diodes, the allowed maximum reverse voltage applied at 100 - 125 degC, cannot be applied above 150 degC, without instability of the electrical characteristic and risk of failure. In the case of similar standard recovery diodes, the same allowed maximum reverse voltage can be applied from 100 degC up to 175-200 degC junction temperature without instability. The instability manifested by visible thermal runaway of the electrical characteristic to higher and higher values of reverse current, is caused by the surface component flowing at the junction edge. Damage at the junction periphery has been found for the failed devices after instability. Performance improvement of fast recovery diodes at high temperature is possible by further reduction of the surface leakage current