Carrier lifetime modulation on current capability of SiC PiN diodes in a pulsed system.

Silicon carbide (SiC) PiN diode has shown substantial promise as the freewheel diode for switch protection in a pulsed system. In this paper, we investigate the carrier lifetime (τ) modulation on pulsed current capability of SiC PiN diodes. The carrier lifetime in 4H-SiC is modulated by the generation of the Z center through neutron irradiation. Surprisingly, we found that the pulsed current of SiC PiN diodes shows a limited improvement when the carrier lifetime (τ) increases from 0.22 to 1.3 μs, while is significantly promoted as the carrier lifetime increases from 0.03 to 0.22 μs. This changing trend is obviously different from the on-state resistance, which decreases with the increased carrier lifetime. The simulation result indicates that the heat generation (i.e., maximum temperature rise) inside the PiN diodes, especially in the drift layer, is remarkably aggravated in the pulse tests for τ < 0.1 μs, but which is significantly suppressed as carrier lifetime rises to 0.2 μs and above. Therefore, the dependence of pulsed current on carrier lifetime is ascribed to the heat generation resulting from the carrier lifetime controlled conductivity modulation effect, which hence affects the temperature rise and brings about the failure of SiC PiN diodes under high pulsed current.