Calculation of the power capabilities of HBT amplifiers based on a new physical HBT model

Abstract

A novel model for the simulation of the microwave power capabilities of HBTs is presented. The model is based on physical analytical formulation of the terminal currents as functions of the base‐emitter and base‐collector voltages. It takes into account the unequal thermal distribution of temperature for multifinger HBT devices, the impact ionization, tunnelling, recombination currents, etc. From the simulation of multi‐finger transistor structures it can be concluded that high thermal device resistances are detrimental for power performance, because of the unequal distribution of temperature and, hence, base current in the HBT structure. In can also be concluded that the input and output reflection coefficients are insensitive to temperature variation. Finally, it has been shown theoretically and experimentally that the breakdown voltage increases slightly with increasing operating temperature. © 1996 John Wiley & Sons, Inc.

A high-power and high-gain X-band Si/SiGe/Si heterojunction bipolar transistor

“…Usually, the junction temperature in the center of the device is higher than that at the edges. The nonuniform temperature distribution deteriorates the power performance by rendering the center part of the device useless for high-power operation [16]. As a consequence, a high breakdown voltage with low current density, which can be obtained by designing a thick and lightly doped collector layer (limited by the Kirk effect), is preferred for power HBT design.…”