Short Circuit Robustness of 1200 V SiC Junction Transistors and Power MOSFETs

Abstract

Short-circuit (SC) robustness of 1200 V-rated SiC npn Junction Transistors (SJTs) and commercial power DMOSFETs is investigated. Due to low (2x) overdrive base currents and low short-circuit currents, SJTs demonstrate superior SC capability including: (a) minimum short-circuit withstand time (tSC) of 14 µs, even at VDS=1000 V (b) Perfectly stable output and blocking characteristics after 10,000, 10 µs long SC pulses at 800 V, (c) tSC ≥ 18 µs at 800 V up to (at-least) 175°C base-plate temperatures. In contrast, commercial (Gen-II) 1200 V/80 mΩ SiC MOSFETs exhibit catastrophic failure beyond tSC = 7 µs at 500 V, and tSC = 3 µs at 800 V, due to excessive SC currents of > 200 A resulting in junction temperatures in excess of 650°C. The MOSFET’s drain leakage current increases by a factor of 120, and the VTH reduces by 20%, after 7 µs-long SC pulses at 500 V.