A 4H-SiC high-power-density VJFET as controlled current limiter

Considering fault current limiters for serial protection, many structures exist, from regulation to other complex systems such as circuit breakers, mechanical switches, or more conventional fuses. Up to now, only a few semiconductor current limiter structures have been described in the literature. Although current-regulative diode components already exist, their voltage and current capabilities (V_BR=100 V, I_max=10 mA), do not allow their use in power systems. This paper presents both simulation study and experimental results of a bidirectional current limiter structure based on a vertical SiC VJFET. The device was designed for serial protection in order to limit I²t value. Finite-element simulations were performed with ISE-TCAD software to design the device and evaluate its static electrical characteristics. Then, dynamic simulations were performed to underline current reduction ability and power losses adjustment by gate resistance value optimization. Finally, electrical characterization for a unidirectional and a bidirectional device were done up to 400 V. The measured specific on resistance R_ON is in the range of 176 mΩ·cm². Limiting capabilities have also been measured for a bidirectional device made of two unidirectional devices connected head to tail. The highest breakdown voltage value in "current limiting state" was measured to be ∼810 V, corresponding to a high power density of 140 kW/cm².