650-V Normally-off GaN/SiC Cascode Device for Power Switching Applications

A 650-V/84-m normally-off GaN/SiC cascode device is demonstrated with systematic static and dynamic characterizations. The cascode device features a low voltage enhancement-mode (E-mode) GaN-HEMT to enable normally-off gate control, and a 650 V normally-on SiC JFET provides the high-voltage blocking capability. The GaN/SiC cascode device exhibits many application-desired behaviors, including reverse conduction capability, avalanche breakdown capability, thermally stable threshold voltage, low input/output capacitances, no dynamic RON degradation, and negligible dynamic VTH shift. In addition, a customized double-pulse test board is built to evaluate the switching performance of this cascode device and other 650-V SiC-based power devices. This cascode device adopting low-voltage GaN HEMT has low QGRON and exhibits excellent switching performance. The switching losses (EON and EOFF) are much smaller than that of 650-V Si/SiC cascode device and comparable to that of the state-of-the-art 650-V SiC MOSFETs.