Doping-less Bipolar Transistor with fT Surpassing that of Conventional BJT

K. Nadda, M. Jagadesh Kumar
Indian Institute of Technology Delhi, IN

Keywords: bipolar charge plasma transistor, silicon-on-insulator, current gain, simulation, cut-off frequency, CMOS technology

Summary:

An innovative ultrathin SOI based bipolar charge plasma transistor BCPT for RF circuit applications is presented in this paper. The proposed device structure exhibits high cut-off frequency and an improved current drive while still maintaining an inherent super high current gain beta of the BCPT. Together with the improved RF characteristics, super high beta, and the fact that the BCPT is fabricated with low thermal budgets neither by doing ion-implantation nor by diffusing any impurities into the SOI layer, the proposed BCPT structure becomes a viable option for the future nano-scale BJTs in the BiCMOS technology. The BCPT has metal electrodes with different work-functions (φm,E < φSi, φm,C < φSi and φm,B > φSi ), to induce (i) electrons for forming the emitter and the collector region and (ii) holes to form the base region on an undoped SOI layer. In conclusion, a doping-less bipolar transistor is realized that surpasses the dc as well as the AC characteristics of the conventional BJT. This concept can be further explored for realizing BJTs on materials like poly-silicon and laying the foundation for system-on-glass topology.