A Combined Model With Electrothermal Coupling and Electromagnetic Simulation for Microwave Multifinger InP-Based DHBTs

This paper presents a combined model with electrothermal coupling and electromagnetic (EM) simulation for multifinger InP-based double heterojunction bipolar transistors (DHBTs). The electrothermal coupling effect, which occurs in multifinger InP DHBTs, is characterized based on 3-D thermal simulation. In addition, EM simulation technique is presented to account for the distributed effect of interconnection of the fingers and their surroundings. A large-signal model for single-finger DHBTs is implemented as a seven-port symbolically defined device, which accounts for several physical phenomena, including the self-heating effect, Kirk effect, current blocking effect, mobile charge modulation of the base-collector capacitance, and velocity field modulation in the transit time. The combined model implemented in Agilent-ADS is verified by comparing the simulated and measured data in dc small-signal
S
-parameters and large-signal microwave power characteristic. This approach allows a simple method to analyze and predict microwave multifinger InP DHBTs for power amplifier circuit design using commonly available computer-aided design tools such as Agilent-ADS.