Improvement of Current Gain and Breakdown Voltage in 4H-SiC BJTs Employing High-k Dielectric as an Interfacial Layer

Abstract

This paper proposes a new structure of 4H-SiC bipolar junction transistor, which can both achieve high current gain and high open base breakdown voltage. By introducing a groove type of metal-high k dielectric-silicon carbide (MIS) structure into the active region along the base-emitter sidewall which is formed with the process of isolation etching, a large electric field appears at the interface between high-k dielectric and bulk material by analyzing the potential distribution in forward mode, thus accelerating the electron transport. Based on a doping concentration of 4×1017cm-3 and thickness of 0.6um base region, current gain of as high as 191 is obtained using TCAD simulation, and that is almost double of the conventional structure in the same simulation setup. Furthermore, a field plate structure is composed combined with the base contact metal simultaneously, and the open base breakdown voltage is obviously increased from 634V to 948V with a 6μm-thick n-SiC collector (Nd=3×1015cm-3).