Cathode-Side Current Filaments in High-Voltage Power Diodes Beyond the SOA Limit

TCAD simulation of current filamentation in adjacent IGBT cells under turn-on and turn-off short circuit condition

“…During this phase, several kinks are observed in the v CE waveform in conjunction with a rapid increase of T j max . This is an indication of the onset of current filaments [2]. Fig.…”

“…current filamentation) occurs, because such an effect induces strong local self-heating and restrict the turn-off capability of the switch. In previous works [1][2][3], strong collector side electric field strength (E collector ) is claimed to be one of the relevant factors for the onset of current filaments. However, cause-effect relationship between E collector and filamentation has never been completely clarified.…”

Influence of carrier lifetime distribution on the current filament in high voltage diode

“…This is because the plasma layer at the anode side for the diodes D2 and D3 is extracted faster than that of the diode D1, and the depletion layer at p + n − junction is built up earlier. However, over a short time, the dynamic avalanche has occurred at p + n − junction due to a high di/dt (10 kA/μs), and a negative differential resistance appears at the anode side because of a space modulation effect of the electric field gradient by the free charge carriers [4], leading to the earlier appearance and non-uniform distribution of the current density.…”

“…Therefore, the dynamic avalanche will occur, even the voltage is much lower than the static breakdown voltage [15,16]. In [4], the differences between the formation reasons and the variation behaviors of cathode side and anode side filaments were explained by analyzing the plasma front velocities during reverse recovery, and the results have shown that the filaments at the anode and cathode sides are both relevant to the negative differential resistance (NDR) in the I-V characteristic. After the plasma layer disappears, the current filament will connect the anode and cathode through the whole diode to maintain a positive feedback process in the impact ionization regions of both sides.…”

“…Recent studies have shown that the appearances of the filaments at the anode and cathode sides do not necessarily lead to the diode destruction, however, the eventual filament by a transition from avalanche-induced into thermally driven filament could cause the local temperature rise inside the device, this is an important factor of the device failure [3][4][5]. In order to improve the fast and soft recovery characteristic of high voltage diode, some technologies by improved structures and carrier lifetime controls were implemented.…”