The MOS-depletion-mode-thyristor: a new MOS controlled bipolar power device

A novel MOS gate-controlled thyristor device is discussed. In these depletion-mode thyristors (DMTs), the depletion region formed by the application of a gate bias across an MOS gate is utilized to divert the current flowing in a thyristor element into a transistor element. This process turns off the device because the transistor element derives its base current from the thyristor element. The DMT offers the following attributes: (1) low forward voltage drop in the on-state at high current densities due to conduction via the thyristor element; (2) high-input-impedance MOS gate control, and (3) equivalent performance for complementary (n- and p-channel) devices. Experimental verification of the operation of the DMT devices has been achieved by the fabrication of 600-V devices using a trench (UMOS) gate technology. The forward conduction current density of the device was measured to be five times higher than that of the insulated-gate bipolar transistor at a forward drop of 1 V. Computer simulation of the forward conduction of the DMT indicates that its performance approaches that of a one-dimensional thyristor. The MOS gate controlled current turn-off under high-voltage DC switching has been demonstrated at current densities in excess of 5000 A/cm²