Simulation and design of InGaAsN-based heterojunction bipolar transistors for complementary low-power applications

The performance capabilities of pnp InGaAsN-based heterojunotion bipolar tr ansistors (HBTs) for use in complementary NET technology have been theoreti cally addressed with a two-dimensional simulation program based on the drif t-diffusion model. Simulation results closely reproduce the DC characterist ics experimentally observed from the first demonstrated pnp AlGaAs/InGaAsN HBT with a current gain of Is and a turn-on voltage around 0.89 V. Numerous design approaches have been explored to maximize the transistor performanc es. As a result, a substantial improvement of the DC current gain (by a fac tor of 2-3) and high-frequency operation performances (with f(T) and f(MAX) values up to 10 GHz) can be easily achieved with the proper use of varying base thickness X-B and dopant-graded base. The effect of the quaternary ba nd-gap value E-G is also addressed. Simulation results show that pup device with turn-on voltage similar to 0.7 V can be produced by lowering E-G to 1 .0 cV, without any important degradation of DC and RF properties, because h ole transport at the emitter/base side is not strongly affected. The replac ement of the InGaAsN collector by GaAs is finally reported. Comparable DC a nd improved RF simulated performances are observed fr om this double HBT st ructure that takes advantages of the negligible valence band offset at the base/collector interface. These encouraging performances demonstrate the pr acticability of using InGaAsN-based HBTs for complementary low-power applic ations. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.