All-WBG Cascode Device with p-GaN Gate HEMT and SiC JFET for High-Frequency and High-Temperature Power Switching Applications

An all-wide-bandgap (all-WBG) cascode device with a low-voltage (LV) enhance-mode (E-mode) p-GaN gate HEMT as the control device and a high-voltage (1IV) depletion-mode (D-mode) SiC JFET as the voltage blocking device has been systematically studied. The demonstrated device with a breakdown voltage (BV) rating of 1200 V and a static ON resistance (R_ON) of 100 mΩ, features small device capacitances, avalanche breakdown capability, thermally stable threshold voltage (V_TH), no dynamic RON degradation, and small gate charge (Q_G). To identify its safe operation in the OFF-state with a high drain bias, the OFF-state middle point voltage (V_M) between the E-mode device drain and D-mode device source is investigated. An adequately low OFF-state V_M is achieved under both static and dynamic modes. Furthermore, a double-pulse test circuit is built to evaluate the transient switching performance at 25 °C and 150 °C. Under 800-V/16-A testing conditions, high switching speed with low total switching losses of 214 μJ and 236 μJ are obtained at 25 °C and 150 °C, respectively.