Thin-drift-layer n-channel 4H-SiC IGBT with low switching loss and switching ringing reduction

Abstract

An n-channel 4H-SiC insulated-gate bipolar transistor (IGBT) with an extremely low switching loss was demonstrated by making 70 μm thin drift layers designed for 6.5 kV blocking voltage, without substrates. A conductivity-modulated bipolar operation was successfully performed as a on-voltage of 4.96 V at a 100 A cm−2 collector current. The turn-off losses under 3.6 kV/32 A operation were 8.8 (at room temperature) and 22.7 mJ (at 150 °C), which were much lower than the estimated losses of SiC IGBTs with thick drift layers. A detailed investigation on turn-off transition of SiC IGBTs specifically focused on a voltage-slope increase was also conducted. This phenomenon can cause ringing in switching characteristics. A device structure has been proposed to eliminate it by controlling the expansion of a depletion layer. Voltage-slope control and ringing reduction without noticeable degradation in static characteristics and switching loss were demonstrated with the SiC IGBT with the proposed device structure.