Electrothermal characteristics of second breakdown in diodes under the EMP stress

2D transient electrothermal simulations are carried out of the second breakdown in a diode with a p-n-n⁺ structure under the EMP stress. The paper begins with a study of the variations of the electric field and the current density distribution in a diode as well as the terminal voltage and the terminal current with the time duration of the EMP stress, followed by a research on the variations of the trigger temperature, trigger current and trigger energy with the delay time of the second breakdown. The research results show that the second breakdown in diodes is caused by the thermal effect, and that the current concentration is not its necessary condition. In addition, the triggering temperature and triggering current increase with a decrease in the delay time, while the triggering energy decreases with a decrease in the delay time. Computational permanent damage threshold energies of the diode are in good agreement with experimental data.