Comprehensive Assessment of Failure Mechanism of Glass-Encapsulated Pulse PiN Diode under Pulse Condition

Glass-encapsulated pulse PiN diode (GED) is one of the important devices in pulsed power systems. Irreversible deterioration or even failure may occur in GEDs under long-term pulse conditions and endanger the safety of the pulse power system. In this paper, a comprehensive assessment of the failure mechanism of GED is conducted by life experiments and failure analysis. The results show that breakdown and forward conduction voltage (V_F) drop are two major deterioration phenomena of GED under pulse conditions. The breakdown and the V_F drop should have different mechanisms because of the weak correlation between the two phenomena. During the turn-off of GED with high di/dt and loss, a dynamic avalanche occurs at the N + n- junction side which produces current filaments and triggers a thermal runaway resulting in breakdown. During the turn-on of GED with high current density, defects multiply the current density by 2 ~ 4 times and trigger a thermal runaway which would stop when turned off resulting in partial chips failure and V_F drop.