Suitability of N-ON recessed implanted gate vertical-channel SiC JFETs for optically triggered 1200 V solid-state-circuit-breakers

Abstract

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 JFETs, designed for high-power bidirectional (four quadrant) solid-state-circuit-breaker 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 FWHM was 1.8 μs. 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 solid-state-circuit-breaker, based on these rugged JFET, is proposed.