The performance capabilities of pnp InGaAsN-based heterojunotion bipolar transistors (HBTs) for use in complementary NET 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 Is 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 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 band-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 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 fr om 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.