Characerization on Performances and Avalanche Capability of Super Cascode Switch Based on GaN HEMT

A Super Cascode switch comprising a GaN HEMT and parallel SiC JFETs is proposed and experimentally characterized in this paper, covering the basic performances and UIS characteristics. By cascading a single GaN HEMT with multiple parallel SiC JFETs, the structure not only combines SiC's high breakdown voltage with GaN's high-speed switching, but also addresses the driving and safety issues caused by the normally-on SiC JFET, just as traditional Cascode. What’s more important is the current capability is significantly enhanced. Our experiment reulsts on double-pulse testing show that the voltage change rate of the Super Cascode switch is as high as 79–114 V/ns at the dc-bus voltage between 200V and 400V, while the switching loss is only slightly increased by parallel JFETs. Furthermore, it’s experimentally confirmed that symmetrical layouts enhance current sharing, while asymmetric designs cause uneven initial conduction. UIS testing indicats that the avalanche energy tolerance is largely improved by multiple parallel JFETs. The study conducted in this paper provides useful guidances for applying the proposed Super Cascode switch in high-voltage, high-frequency scenarios.