SI HETEROBIPOLAR TRANSISTOR WITH A FLUORINE-DOPED SIC EMITTER AND A THIN, HIGHLY DOPED EPITAXIAL BASE

We examined fluorine doping to improve SiC/Si heterojunction bipolar transistors. We present the film properties of the fluorine-doped SiC and a device characteristics of an HBT using the SiC emitter and a 50-nm-thick, highly doped epitaxial base (1019/cm3). The current gain was improved from 15 to 80 by doping with fluorine. The current gain was four times larger than that of a conventional poly-Si emitter homo-transistor with the same base structure. In spite of the very thin base, the Early voltage was over 100 V. Forward-bias tunneling current was hardly seen at the emitter-base junction. The role of fluorine appears to terminate the dangling bonds. The results show the possibility of fabricating transistors with a very thin, highly doped base. © 1990 IEEE