Self-heating and loss of thermal stability under a single current surge pulse in high-voltage 4H-SiC rectifier diodes

Abstract

Self-heating and loss of thermal stability under the action of a single 8 ms current surge pulse has been studied experimentally in high-voltage (6 kV class) 4H-SiC p+–n–n+ rectifier diodes up to current densities of j ∼ 9000 A cm−2. In spite of the very strong self-heating and appreciable loss of thermal stability, the diode structures withstand two to three surge pulses of this kind. At extremely high current densities, a dynamic instability of the N type is observed: the current decreases despite that the bias applied to the structure increases. The two-dimensional thermo-electric model describes experimental results quite well up to current densities of j ∼ 5000 A cm−2, which correspond to a diode base temperature at the end of the pulse equal to 1100 K. At even higher j, the discrepancy between the results of theoretical calculations and experimental data becomes rather important; nevertheless, a qualitative agreement between the calculations and experiments is observed up to the maximum values of j.