Publications
Simulation and design of InGaAsN-based heterojunction bipolar transistors for complementary low-power applications
The performance capabilities of pnp InGaAsN-based heterojunction bipolar transistors (HBTs) for use in complementary HBT technology have been theoretically addressed with a two-dimensional simulation program based on the drift-diffusion model. Simulation results closely reproduce the DC characteristics experimentally observed from the first demonstrated pnp AlGaAs/InGaAsN HBT with a current gain of 18 and a turn-on voltage around 0.89 V. Numerous design approaches have been explored to maximize the transistor performances. As a result, a substantial improvement of the DC current gain (by a factor of 2-3) and high-frequency operation performances (with fT and fMAX values up to 10 GHz) can be easily achieved with the proper use of varying base thickness XB and dopant-graded base. The effect of the quaternary band-gap value EG is also addressed. Simulation results show that pnp device with turn-on voltage approximately 0.7 V can be produced by lowering EG to 1.0 eV, without any important degradation of DC and RF properties, because hole transport at the emitter/base side is not strongly affected. The replacement of the InGaAsN collector by GaAs is finally reported. Comparable DC and improved RF simulated performances are observed from this double HBT structure that takes advantages of the negligible valence band offset at the base/collector interface. These encouraging performances demonstrate the practicability of using InGaAsN-based HBTs for complementary low-power applications.