Simulation of a Short-Circuit Rugged Trench IGBT with a JFET Connected to a SiC Schottky Rectifier

Abstract

The conduction losses of trench insulated-gate bipolar transistors (TIGBTs) can be reduced using a larger channel width, but their short-circuit ruggedness degrades without taking an appropriate countermeasure. Here, we propose a short-circuit rugged TIGBT (SCR-TIGBT) with a silicon carbide Schottky diode (SiC-SD) connected to highly doped p-regions below the trenches. The p-regions form a junction field effect transistor (JFET). The SiC-SD clamps the voltage drop along the channel, and the saturation current of the SCR-TIGBT with the larger channel width is indeed reduced. In order to estimate the performance benefit, we perform simulations and compare to a benchmark TIGBT with similar short-circuit ruggedness. We find a reduction of the saturation collector-emitter voltage by 480 mV for a fixed collector doping concentration and 550 mV for fixed switching losses. The benefit originates from a strongly reduced voltage drop along the MOS channel while the large forward voltage drop of the SiC-SD retains the stored charge and voltage drop in the drift region of the SCR-TIGBT.