Thermal Stability of Silicon Carbide Power JFETs

Abstract

9 pagesInternational audienceSilicon carbide (SiC) JFETs are attractive devices, but they might suffer from thermal instability. An analysis shows that two mechanisms could lead to their failure: the loss of gate control, which can easily be avoided, and a thermal runaway caused by the conduction losses. Destructive experimental tests performed on a dedicated system show that the latter mechanism is more severe than initially expected. A low thermal resistance and gate driver equipped with protections systems are thus required to ensure safe operation of the SiC JFETs

Comparative evaluation of the short-circuit withstand capability of 1.2kV silicon carbide (SiC) power transistors in real life applications

“…However, the SiC JFET control is regained once the breaker clears the fault, suggesting there is no destruction of the junction. In fact, loss of the turn-off capability is attributed to the increase of the punch-through gate-source voltage with high temperatures [23,24]. As a result, the window between the threshold voltage and the punch-through voltage gets narrower with increasing short-circuit duration.…”

Modulator for five-phase voltage-source inverters

“…However, the SiC JFET control is regained once the breaker clears the fault, suggesting a latch-up phenomenon exists rather than destruction of the junction. In fact, loss of gate control is attributed to the increase of the punch-through gate-source voltage with high temperatures [19], [20]. As a result, the window between the threshold voltage and the punch-through voltage gets narrower with increasing short circuit duration.…”

Packaging with Double-Side Cooling Capability for SiC Devices, Based on Silver Sintering

“…However, despite their inherent capability to operate at high temperature, which originates from the large energy band-gap of SiC [4], SiC JFETs are prone to thermal runaway [5] (this would also be true of other unipolar devices such as Schottky diodes [6] or MOSFETs): as their on-state resistance (R DSon ) increases strongly with the temperature (R DSon ∝ T 2.4 or more [7]), so do their losses. If insufficient cooling is provided to the JFET, this yields to a race condition in which increasing losses result in ever higher junction temperature.…”

“…As a consequence, these devices must be attached to an efficient thermal management system: thermal resistances of around 1 K/W are required [7], even though the temperature of the ambient air surrounding the converter can be as high as 200°C or more.…”