600 V dual gate MCT structures

Abstract

Power MOS-gated thyristors such as the BRT and MCT have low on-state voltage drops but do not possess the current saturation feature that is present in the IGBT. Dual Gate devices have been proposed to overcome this problem by adding the IGBT mode of operation to devices that operate as thyristors in the on-state, through the use of two independently biased gates. The 600 V Dual-Gate BRT (DG-BRT) has been experimentally demonstrated to have a lower forward voltage drop than the IGBT but its FBSOA was found to be considerably worse. The Dual-Gate MCT (DG-MCT) device, described for the first time in this paper, also possesses two modes of operation. In the thyristor mode, a thyristor region in the DG-MCT conducts current, leading to a low on-state voltage drop. The device can be switched to the IGBT mode by changing the bias on one of the gates. In this mode, the DG-MCT possesses a superior FBSOA to the DG-BRT because it uses an N-channel MOSFET to shunt current across a P-N junction to prevent latchup of the thyristor, instead of a P-channel MOSFET used in the DG-BRT. The device has the ability to saturate current even at high anode voltages in the IGBT mode. The DG-MCT, therefore, has fast switching speed, controlled turn-on and turn-off capability, and a wide safe operating area. The results obtained using simulations and by measurements on fabricated devices are reported in this paper.