Safe operating area and failure modes of SiC gate turn-off thyristors for high energy applications

Date

2014-08

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Abstract

In order to determine the safe operating limits of SiC 9 kV SGTOs a test system was designed and built to stress the devices with high current density pulses (over 10X the rated densities) for greater than 10,000 high current discharges. A total of 7 SiC SGTOs were pulsed on the test system for over 250,000 pulses total. The data from these pulses is then used to calculate the device performance. The DC characteristics were monitored as part of the automated test system as well as on an Agilent B1505A high power device analyzer. Using a combination of the switching characteristic information as well as the DC characteristic curves it was determined that for 100 µs square pulses the devices could operate without failure up to 2.0 kA for an extended amount of time (>> 10,000 shots). Above 2.0 kA the device characteristics degrade rapidly. The cause of this degradation is explored in order to identify the primary failure modes associated with operating these devices at such high current densities. The cause of the observed failures are partially due to packaging breakdown at high currents as well as a permanent reduction in high level lifetime and mobility of minority carriers. Based off the current body of knowledge it is postulated that the observed reduction is due to the formation of stacking faults in the device which serve as deep level traps for the minority carriers.

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Keywords

Silicon carbide (SiC), Thyristors, SGTO, High current density, Failure mode, Safe operating area (SOA)

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