Suitability of N-ON Recessed Implanted Gate Vertical-Channel SiC JFETs for Optically Triggered 1200 v Solid-State Circuit Breakers

A requirement for the commercialization of power SiC transistors is their long term reliable operation under the hard-switching conditions and high temperatures encountered in the field. Normally ON 1200 V vertical-channel implanted-gate SiC junction field effect transistors (JFETs), designed for high-power bidirectional (four quadrant) solid-state-circuit-breaker (SSCB) applications, were repetitively pulse hard switched at 150 °C from a 1200 V blocking state to an ON-state current of 115 A, which is in excess of 13 times the JFET's 250-W/cm² rated current at 150 °C. The JFETs were fabricated in seven photolithographic levels with a single masked ion-implantation forming the p+ gates and guard rings, and with no epitaxial regrowth. The pulsed testing was performed using a low inductance RLC circuit. In this circuit, energy initially stored in a capacitor is discharged in a load resistor through the JFET under test. The JFET hard-switch stressing included over 2.4 million 1200 V/115-A hard-switch events at 150 °C and at a repetition rate of 10 Hz. The peak energies and powers dissipated by the JFET at each hard-switch event were 73.2 mJ and 68.2 kW, respectively. The current rise rate was 166 A/μs and the pulse full width at half maximum (FWHM) was 1.8μs. After over 2.4 million hard-switch events at 150 °C, the JFET blocking voltage characteristics remained unchanged while the ON-state conduction slightly improved, which indicate reliable operation. An optically triggered SSCB, based on these rugged JFET, is proposed.