High-Current-Gain SiC BJTs With Regrown Extrinsic Base and Etched JTE

Abstract

This paper describes successful fabrication of 4H-SiC bipolar junction transistors (BJTs) with a regrown extrinsic base layer and an etched junction termination extension (JTE). Large-area 4H-SiC BJTs measuring 1.8 times 1.8 mm (with an active area of 3.24 ) showed a common emitter current gain of 42, specific on-resistance of 9 , and open-base breakdown voltage of 1.75 kV at room temperature. The key to successful fabrication of high-current-gain SiC BJTs with a regrown extrinsic base is efficient removal of the regrown layer from the surface of the emitter-base junction. The BJT with regrown layer has the advantage of lower base contact resistivity and current gain that is less sensitive to the distance between the emitter edge and the base contact, compared to a BJT with ion-implanted base. Fabrication of BJTs without ion implantation means less lifetime-reducing defects, and in addition, the surface morphology is improved since high-temperature annealing becomes unnecessary. BJTs with flat-surface junction termination that combine etched regrown layers show about 250 V higher breakdown voltage than BJTs with only etched flat-surface JTE.